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Scientific Data Documentation

National Survey of Ambulatory Surgery, 1995

1995 National Survey of Ambulatory Surgery (NSAS)
Public Use Data Tape Documentation

Abstract

This material provides documentation for users of the 1995 NSAS Public Use Data Tape. The NSAS was implemented by the National Center for Health Statistics (NCHS) in 1994. It covers ambulatory surgery procedures performed in hospitals and free-standing ambulatory surgery centers in the United States.

Section I describes the survey and includes information on the history and scope of the NSAS; the survey methodology, data collection and medical coding procedures; population estimates, measurement errors, and sampling errors.

Section II provides technical details of the tape.

Section III provides a detailed description of the contents of each data record.

Appendix A defines certain terms used in this document;
Appendix B contains the ICD-9-CM Addenda;
Appendix C provides population estimates to allow the user to calculate rates; and
Appendix D provides unweighted and weighted frequencies for selected descriptive variables.

I. Description of the National Survey of Ambulatory Surgery

Introduction--This document describes the 1995 National Survey of Ambulatory Surgery (NSAS) and provides information for users of the 1995 NSAS public use data file. This survey, conducted by the National Center for Health Statistics (NCHS) and implemented in 1994, covers ambulatory surgery procedures performed in hospitals and in free-standing ambulatory surgery centers in the United States. A brief description of the survey design and data collection procedures is given below. A more detailed description of the survey design, data collection procedures, and the estimation process has been published (1).

History--The National Survey of Ambulatory Surgery was undertaken to obtain information about the use of ambulatory surgery. Ambulatory, or outpatient, surgery has increased in the United States since the early 1980's. Two major reasons for this increase were advances in medical technology and cost containment initiatives.

On the medical side, many surgeries performed for hospital inpatients have moved to outpatient settings, in part because improvements in anesthesia and better analgesics for relief of pain have made surgery less complex and risky (2). Also, minimally invasive and non-invasive procedures, such as laser surgery, laparoscopy, and endoscopy, have been developed and are being performed with increasing frequency.

On the cost side, concern about rising health care costs led to changes in the Medicare program that encouraged the use of ambulatory surgery (3). In 1982 the Medicare program was expanded to cover care in ambulatory surgery centers. In 1983, a prospective payment system based on diagnosis-related groups (DRG=s) was adopted for hospital inpatient care. This system created strong financial incentives for hospitals to perform less complex surgery in an ambulatory setting. In the mid-1980's, the peer review organizations for Medicare established outpatient settings as the norm for certain surgeries and denied Medicare payment for hospital admissions deemed inappropriate or medically unnecessary. Many State Medicaid plans and private insurers followed the lead of the Medicare program and adopted similar policies.

As these changes went into effect, freestanding ambulatory surgery centers increased in number, from 239 centers that performed 380,000 procedures in 1983, to over 1,800 centers performing more than 3.2 million procedures ten years later (4). The number of ambulatory surgery procedures done in hospitals and freestanding settings combined rose from 5.4 million in 1983 to 16.2 million in 1993 (5).

The National Hospital Discharge Survey (NHDS), which has been conducted by the National Center for Health Statistics every year since 1965, includes information on procedures performed on inpatients (6). The NHDS remains a good source of data for surgical procedures, such as open-heart surgery or cesarean sections, that must be done on an inpatient basis. But for surgeries that can be performed on an ambulatory basis, NHDS estimates are incomplete. Thus the National Survey of Ambulatory Surgery was undertaken to provide data on the increasing use of this type of health care.

SURVEY METHODOLOGY

Source of the Data--The NSAS covers ambulatory surgery procedures performed in hospitals and free-standing ambulatory surgery centers (FSASC). The hospital universe includes noninstitutional hospitals exclusive of Federal, military, and Department of Veterans Affairs hospitals, located in the 50 States and the District of Columbia. Only short-stay hospitals (hospitals with an average length of stay for all patients of less than 30 days) or those whose specialty is general (medical or surgical) or children=s general are included in the survey. These hospitals must also have six beds or more staffed for patient use. The universe definition is the same as that used for the National Hospital Discharge Survey. The sampling frame for the hospital universe consisted of eligible hospitals listed in the 1993 SMG Hospital Market Database (7).

The universe of freestanding facilities includes FSASCs that are regulated by the States or certified by HCFA, the Health Care Financing Administration, for Medicare participation. The sampling frame consisted of facilities listed in the 1993 Freestanding Outpatient Surgery Center Database (8) and Medicare-certified facilities included in the HCFA Provider-of-Services (POS) file (9). Facilities specializing in dentistry, podiatry, abortion, family planning, or birthing are excluded. However, these procedures are not excluded from in-scope locations.

Sample design and data collection--The NSAS samples facilities using a multi-stage probability design with some facilities selected with certainty and others sampled with varying selection probabilities. Independent samples of hospitals and free-standing ambulatory surgery centers were drawn. The sample includes with certainty facilities which perform a high volume of ambulatory surgeries annually. Non-certainty facilities are selected using a stratified, cluster design, where the clusters are 198 primary sampling units (PSUs) that comprise the sample of PSUs used in the 1985-1995 National Health Interview Survey (NHIS). PSUs are counties or groups of counties, or county equivalents, or towns and townships (the latter in New England and Hawaii).

Noncertainty facilities were stratified by facility type (hospital versus freestanding), ambulatory surgery status of hospitals (i.e. whether or not the hospital performed such surgery), facility specialty, and geographic region. From each stratum containing fewer than six facilities, up to three facilities were selected by means of systematic random sampling, with selection probabilities proportional to size, where size is the number of ambulatory surgeries performed annually. For strata containing six or more facilities, first stage sampling involved selection of 112 PSUs, which are a probability subsample of the 198 PSUs in the 1985-94 NHIS sample. Some of these PSUs were sampled with certainty. Selection of noncertainty PSUs was performed within PSU strata defined within the four geographic regions by the number of people in the 1980 Census of Population and NHIS stratification variables. From each PSU stratum, the PSUs were selected with probability proportional to the projected 1985 population. The hospital sample is clustered within a probability subsample of 112 of those PSUs.

The second stage of the cluster design consisted of selection of noncertainty facilities from the sampled PSUs, using systematic random sampling with probabilities proportional to the annual number of ambulatory surgeries performed. For both hospitals and FSASCs, up to three facilities of each type and specialty were selected from each non-certainty PSU and up to 15 facilities were selected across the combined certainty PSUs in each region. For the stratum of hospitals which, according to the sampling frame data, did not have ambulatory surgery, a national sample of 50 hospitals was selected to permit estimates of surgery in hospitals that either change their status or differ from frame data. Any sampled facility which performed less than 50 ambulatory surgeries in the year prior to the data collection year was considered out-of-scope for the data collection year.

Within sampled facilities, a sample of ambulatory surgery visits was selected using a systematic random sampling procedure. Selection of visits within each facility was performed separately for each location where ambulatory surgery is performed. These locations include: main operating rooms, dedicated ambulatory surgery units, cardiac catherization laboratories, laser procedure rooms, endoscopy and laparoscopy rooms, etc. Locations within facilities that specialize in or are dedicated to inpatients, dentistry, abortion, podiatry, pain block, or small procedures are excluded. However, as mentioned above, these procedures are not excluded from in-scope locations.

Following selection of ambulatory surgery visits, data was abstracted from the medical record for each visit. The Medical Abstract Form used in data collection is shown in Figure 1. It contains items relating to the personal characteristics of the patient, including birth date or age, sex, race, zipcode, but not name and address; administrative information, including the date of the surgery, dispostion of the patient, and medical record number; principal and other additional expected sources of payment; and medical information, including diagnoses and surgical and nonsurgical procedures performed, as well as types of anesthesia administered and by whom. The medical record number, date of birth, and patient zip code, are confidential information and are not available to the public.

Response Rate--The 1995 NSAS sample included 333 FSASCs from the 1,732 facilities in the 1993 FSASC sampling frame; and 418 hospitals from the 6,267 listed in the 1993 hospital sampling frame. Of the 751 sampled facilities, 141 were found to be out-of-scope for the NSAS. One hundred twenty-one of the 610 in-scope facilities were nonresponding in 1995. The number of hospitals responding in 1995 was 294, which was 89 percent of the in-scope hospitals. The number of FSASCs responding in 1995 was 195, which represented 70 percent of the in-scope FSASCs.

Medical Coding and Edit--The medical information abstracted from the sampled medical records was coded centrally by NCHS contract staff. A maximum of seven diagnostic codes and six procedure codes was assigned for each sampled abstract. The system currently used for coding the diagnoses and procedures on the medical abstract forms is the International Classification of Diseases, 9th Revision, Clinical Modification, or ICD-9-CM (10).

Following conversion of the data on the medical abstract to computer tape, a final medical edit was accomplished by computer inspection and by a manual review of rejected records. Priority was given to medical information in the editing decision.

Users of the NSAS diagnostic and/or procedure data must take into account annual ICD-9-CM addenda. The addenda lists new codes, new fourth or fifth digits to existing codes, as well as other modifications. Changes go into effect October 1 of the calendar year. However, in order to preserve consistent coding throughout the data year, the NSAS coding for 1995 data is consistent with the ICD-9-CM and the Addenda through October 1, 1994. Appendix B lists the changes for 1986 through 1994.

Population Estimates--Appendix C shows population estimates provided by the U.S. Bureau of the Census. The estimates are of the U.S. civilian resident population on July l of the data year. These population estimates are consistent with those published in Current Population Reports, Series P-25; however, they are not official population estimates of the Bureau of the Census.

Measurement Errors and Limitations of the Data--As in any survey, results are subject to nonsampling or measurement errors, which include errors due to facility nonresponse, missing abstracts, information incompletely or inaccurately recorded on abstract forms, and processing errors.

In a very small number of records, the age or sex of the patient was missing. For these records, a legitimate value was imputed in such a way as to preserve the original, known distribution of the variable. Fewer than one percent of the records have an imputed age or sex value.

Forty-two percent of the records were missing a value for race of the patient. No attempt was made to impute for these missing values.

Figure 1. Medical abstract for the 1995 National Survey of Ambulatory Surgery

The determination of whether an ambulatory surgery facility is a hospital or a freestanding center is based on the SMG universe from which the facility is selected. In most cases it is apparent whether a facility is a hospital or a freestanding ambulatory surgery center, but some facilities are not easily classified. For example, a Afreestanding@ facility may be owned by a hospital but located some distance away. If such a facility is separately listed in the 1993 SMG Freestanding Outpatient Surgery Center Database and is selected into the NSAS sample from this universe, it is considered a freestanding facility.

The distinction between ambulatory and inpatient surgery is not always clear. According to the 1995 NSAS, an estimated 1.6 percent of ambulatory surgery visits were for patients subsequently admitted to the hospital as inpatients. Some of these patients had procedures which are currently performed exclusively on inpatients, such as coronary artery bypass graft, in addition to diagnostic procedures such as cardiac catheterization. These visits and their suspected Ainpatient@ procedures have not been eliminated from the data file because they are operationally part of the survey design. It is left to the prerogative of the researcher whether or not to include these procedures in an analysis. In NCHS publications for the 1994 NSAS, patients discharged to inpatient status were included in estimates of visits and procedures. For the 1995 NSAS, these visits were excluded from all tabulations.

Sampling errors--Statistics from the NSAS are derived by a multistage estimation procedure that produces essentially unbiased estimates. The estimation procedure has three basic components: (a) inflation by reciprocals of the probabilities of sample selection, (b) adjustment for nonresponse, and (c) population weighting ratio adjustments.

The standard error of a statistic is primarily a measure of sampling variability that occurs by chance because only a sample rather than the entire universe is surveyed. The relative standard error of the estimate is obtained by dividing the standard error by the estimate itself. The resulting value is multiplied by 100, so the relative standard error (RSE) is expressed as a percent of the estimate. Estimates of sampling variability were calculated with SUDAAN software, which computes standard errors by using a first-order Taylor series approximation of the deviation of estimates from their expected values. A description of the software and the approach it uses has been published (11).

Relative Standard Errors for Aggregate Estimates

Table 1 presents parameter estimates to be used in formulae for deriving the approximate relative standard errors for aggregate estimates. To provide error estimates that would be applicable to a wide variety of statistics, numerous variances were calculated and the best fit formula was derived. The formula is based on an empirically determined relationship between the size of an estimate X and its relative variance. The relative standard error is then derived by taking the square root of the relative variance. The relative standard error of an estimate X [RSE(X)], expressed as a percent, may be calculated from the formula:

                                               with a and b provided in Table 1.

For example, in 1995 the estimated number of ambulatory surgery visits to hospitals and free-standing ambulatory surgery centers by persons aged 65 and over with a first-listed diagnosis of cataracts (ICD-9-CM code 366) was 1,893,000 (excluding those vists admitted to hospitals as inpatients). Using the applicable constants from Table 1 for estimates by age produces:
                                             RSE(1,893,000) = 7.08 %

The relative standard error for the estimate of interest is 7.08 percent. From this the standard error is obtained by multiplying the relative standard error by the estimate:

                                             SE(1,893,000) = 1,893,000 * 7.08 % = 134,036

The standard error can be employed to generate confidence intervals for statistical testing. In this example, the 95% confidence interval for the estimate of the total number visits by persons aged 65 and over with a first-listed diagnosis of cataracts is:

                                            (1,893,000 - 2*134,036)<-> (1,893,000 + 2*134,036)

                                              1,624,928<-> 2,161,072

Relative Standard Error for Estimates of Percents

Approximate relative standard errors for estimates of percents may be calculated from Table 1 also. The relative standard error for a percent, 100 p (0<p<1), (expressed as a percent), may be calculated using the formula:

where 100p is the percent of interest, X is the base of the percent, and b is the parameter value, b, given in Table 1.

For example, in 1995 the estimated number of ambulatory surgery visits by persons 65 years old and over was 6,505,000 (excluding those admitted to hospitals as inpatients). This is 33.1 percent of the estimated 19,638,000 visits for that year. Using the applicable constants from Table 1 for estimates by age produces:

                                          RSE (.331) = 0.675%

The relative standard error for the estimate of interest is 0.675 percent. From this the standard error is obtained by multiplying the relative standard error by the estimate:

                                         SE(.331) = .331 * 0.675 % = .0022

The standard error can be employed to generate confidence intervals for statistical testing. In this example, the 95% confidence interval for the estimate of the percentage of ambulatory surgery visits by persons in the 65 and over age group is:

                                         (.331 - 2*.0022) <-> (.331 + 2*.0022)

                                           .327 <-> .335

                                          or, equivalently, 32.7% <-> 33.5 %

Table 1. Estimated parameters for relative standard error formulae for National Survey of Ambulatory Surgery aggregate
             statistics by statistic type: United States, 1995

Characteristic	First-listed Diagnoses		All-Listed Procedures		First-Listed Diagnoses - Hospitals		All-Listed Procedures - Hospital		First-Listed Diagnoses - Freestanding		All-Listed Procedures - Freestanding
	a	b	a	b	a	b	a	b	a	b	a	b
Total	0.00909	562.626	0.00311	631.907	0.01056	570.914	0.00361	657.110	0.03554	165.845	0.01744	185.751
Sex
Male	0.01047	443.044	0.00316	550.551	0.00341	604.130	0.00358	582.511	0.01671	151.962	0.01716	157.168
Female	0.00363	478.144	0.00315	595.095	0.00423	491.716	0.00372	626.102	0.01573	171.346	0.01429	228.421
Age
Under 15 Years	0.00398	292.951	0.00454	324.459	0.00460	297.613	0.00528	338.096	0.02338	90.520	0.01844	168.458
15-44 years	0.00428	367.261	0.00365	518.410	0.00398	515.875	0.00413	566.628	0.01405	165.953	0.01834	163.806
45-64 years	0.00411	491.458	0.00410	490.427	0.00493	537.452	0.00522	507.419	0.01516	139.891	0.01376	190.778
65 years and over	0.00478	442.089	0.00373	468.539	0.00524	500.755	0.00433	506.908	0.02276	133.543	0.01768	175.078
Region
Northeast	0.01262	583.116	0.01175	632.514	0.01416	650.219	0.01570	616.306	0.06337	24.874	0.07134	2.527
Midwest	0.00698	354.739	0.01162	936.993	0.00627	417.906	0.00654	398.770	0.07304	90.986	0.08396	453.098
South	0.01249	382.143	0.01064	388.178	0.01517	341.520	0.01206	412.919	0.02800	180.589	0.03209	155.536
West	0.01356	430.118	0.01417	479.870	0.01585	432.043	0.01866	379.185	0.09046	123.606	0.11146	96.489
Source of Payment
Other Gov,WC	0.01196	247.518	0.01424	254.337	0.01411	277.945	0.01552	306.607	0.02550	97.809	0.03027	136.528
Medicare	0.00575	415.696	0.00469	433.157	0.00652	454.425	0.00589	444.574	0.02592	127.408	0.01800	168.580
Medicaid	0.00798	264.919	0.00968	263.673	0.00760	359.199	0.01099	269.647	0.02084	131.524	0.02300	143.428
Private Insurance	0.00383	517.014	0.00411	544.178	0.00432	548.910	0.00484	586.992	0.01637	177.139	0.01911	178.572
Other,SP,NC,NS	0.02278	361.270	0.02710	340.345	0.03456	423.555	0.04096	368.204	0.03375	98.962	0.04499	21.619

Presentation of Estimates--Publication of estimates for the NSAS is based on the relative standard error of the estimate and the number of sample records on which the estimate is based (referred to as the sample size). Estimates are not presented in NCHS reports unless a reasonable assumption regarding the probability distribution of the sampling error is possible.

Based on consideration of the complex sample design of the NSAS, the following guidelines are used for presenting the NSAS estimates:

If the sample size is less than 30, the value of the estimate is not reported.

If the sample size is 30-59, the value of the estimate is reported but should not be assumed reliable.

If the sample size is 60 or more and the relative standard error is less than 30 percent, the estimate is reported.

If the sample size is 60 or more but the relative standard error is over 30 percent, the estimate is reported but should not be assumed reliable.

How to Use the Data Tape--The NSAS records are weighted to allow inflation to national or regional estimates. The weight applied to each record is found in tape location 21-25. To produce an estimate of the number of visits, the weights for the desired records must be summed.

Appendix D contains unweighted and weighted frequencies for selected descriptive variables on the data tape. These may be used as a cross-check when processing the data on the user's system.

Questions--Questions concerning data on the tape should be directed to Maria Owings, Ph.D., Hospital Care Statistics Branch, Division of Health Care Statistics, National Center for Health Statistics, Presidential Building, Room 956, 6525 Belcrest Road, Hyattsville, Maryland 20782, (301)-436-7125.

REFERENCES

1. McLemore T and Lawrence L. Plan and Operation of the National Survey of   Ambulatory Surgery. Vital and Health
    Statistics, Series 1, No. 37. Hyattsville, MD: National Center for Health Statistics. 1997.

2. New surgical technologies reshape hospital strategies. Hospitals 66(9):30-36, 38, 40-42. 1992.

3. Leader S and Moon M. Medicare trends in ambulatory surgery. Health Affairs Spring: 158-170. 1989.

4. Durant G. Ambulatory surgery centers: surviving, thriving into the 1990's. Medical Group Management Journal 36(2): 16-18,
    20. 1989.

5. SMG Marketing Group, Inc. Outpatient surgery centers exceed 3 million cases. SMG Market Letter 8(5). 1995.

6. Graves EJ and Gillum BS. 1995 summary: National Hospital Discharge Survey. Advance data from Vital and Health
    Statistics; no 278. Hyattsville, Maryland: National Center for Health Statistics. 1996.

7. SMG Marketing Group, Inc. Hospital Market Database. Chicago: Healthcare Information Specialists. April 1993.

8. SMG Marketing Group, Inc. Freestanding Outpatient Surgery Centers Database. Chicago: Healthcare Information
    Specialists. 1993.

9. Health Care Financing Administration. Provider of Services Public Use File. Baltimore: 1993.

10. Public Health Service and Health Care Financing Administration. International Classification of Diseases, 9th Revision,
      Clinical Modification. Washington: Public Health Service. 4th ed. 1991.

11. Shah BV, Barnwell BG, Bieler GS. SUDAAN User=s Manual: Software for Analysis of Correlated Data, Release 6.40.
      Research Triangle Park, NC: Research Triangle Institute. 1995.

II. TECHNICAL DESCRIPTION OF TAPE

Data Set Name------------------------------------------------------BG00.NSAS95.PU
Number of REELS or CARTRIDGES--------------------------------------------------1
Number of Recording Tracks, REEL----------------------------------------------------9
Number of Recording Tracks, CARTRIDGE------------------------------------------18
Density for REEL (bpi)-------------------------------------------------------------6,250
Density for CARTRIDGE (bpi)---------------------------------------------------38,000
Language-----------------------------------------------------------------------EBCDIC
Parity--------------------------------------------------------------------------------Odd
Record Length-------------------------------------------------------------------------97
Block Size-------------------------------------------------------------------------32,689
Number of Records--------------------------------------------------------------121,564

III. RECORD FORMAT:

Location and Coding of Data Elements 

This section provides detailed information for each sampled record on the tape, with a description of each item included in the record. Data elements are arranged sequentially according to their physical location on the tape record. Data are derived from the abstract form; the SMG Hospital Market Tape is an alternative source of data; some items are computer generated.

Item Number	Tape Location	Number of Positions	Item Description and Codes
1	1-2	2	Survey Year: 95
2	3	1	Facility Type: 1=Hospital 2=Free-Standing Ambulatory Surgery Center
3	4	1	Units for Age: 1 = Years 2 = Months 3 = Days
4	5-6	2	Age in years, months, or days: If Units = Years: 0-99* If Units = Months: 01-11 If Units = Days: 00-31
5	7	1	Age Flag: 1 = Value for Age was Imputed 2 = Value for Age was Not Imputed
6	8	1	Sex: 1 = Male 2 = Female
7	9	1	Sex Flag: 1 = Value for Sex was Imputed 2 = Value for Sex was Not Imputed
8	10	1	Race: 1 = White 2 = Black 3 = American Indian/Eskimo 4 = Asian/Pacific Islander 5 = Other 9 = Race Not Stated
9	11	1	Discharge Status: 1 = Routine discharge to customary residence 2 = Discharge to observation status 3 = Discharge to recovery care center 4 = Admitted to hospital as inpatient 5 = Surgery cancelled or terminated 6 = Other, specified 9 = Discharge Status Not Stated
10	12-13	2	Month of Surgery: 01 = January to 12 = December
11	14	1	Geographic Region 1 = Northeast 2 = Midwest 3 = South 4 = West
12	15-16	2	Principal Expected Source of Payment 0 = No Charge 1 = Worker=s Compensation 2 = Medicare 3 = Medicaid 4 = CHAMPUS 5 = Other Government Payments 6 = Blue Cross/Blue Shield 7 = HMO/PPO 8 = Other private or commercial insurance 9 = Self Pay 10 = Other, specified 99 = No expected source of payment
13	17-18	2	Other Additional Source of Payment #1: Same coding as Principal ESOP
14	19-20	2	Other Additional Source of Payment #2: Same coding as Principal ESOP
15	21-25	5	Analysis Weight: Use to Obtain Weighted Estimates
16-25	26-35	10	Type of Anesthesia: 10 types/options 1 = Option Checked 0 = Not Checked/Blank
16	26	1	Type of Anesthesia: Topical/Local
17	27	1	Type of Anesthesia: IV Sedation
18	28	1	Type of Anesthesia: Monitored Anesthesia Care
19	29	1	Type of Anesthesia: Regional, Epidural
20	30	1	Type of Anesthesia: Regional, Spinal
21	31	1	Type of Anesthesia Regional, Retrobulbar block
22	32	1	Type of Anesthesia: Regional, Peribulbar block
23	33	1	Type of Anesthesia: Regional, Block
24	34	1	Type of Anesthesia: General
25	35	1	Type of Anesthesia: Other, specified
26-28	36-38	3	Anesthesia Administrator: 3 givers/options 1 = Option Checked 0 = Not checked/Blank
26	36	1	Anesthesia Administrator: Anesthesiologist
27	37	1	Anesthesia Administrator: Certified Registered Nurse Anesthetist
28	38	1	Anesthesia Administrator: Other Surgeon/Physician
29	39-43	5	Diagnosis ICD9-CM ** Code #1
30	44-48	5	Diagnosis ICD9-CM ** Code #2
31	49-53	5	Diagnosis ICD9-CM ** Code #3
32	54-58	5	Diagnosis ICD9-CM ** Code #4
33	59-63	5	Diagnosis ICD9-CM ** Code #5
34	64-68	5	Diagnosis ICD9-CM ** Code #6
35	69-73	5	Diagnosis ICD9-CM ** Code #7
36	74-77	4	Procedure ICD9-CM ** Code #1
37	78-81	4	Procedure ICD9-CM ** Code #2
38	82-85	4	Procedure ICD9-CM ** Code #3
39	86-89	4	Procedure ICD9-CM ** Code #4
40	90-93	4	Procedure ICD9-CM ** Code #5
41	94-97	4	Procedure ICD9-CM ** Code #6

------------------------------------------------------------------------------------------------------------------

* Ages 100 and over were recoded to 99.

** Codes are in compliance with the International Classification of Diseases, 9th Revision, Clinical Modification, (ICD-9-CM). For diagnosis codes, there is an implied decimal between positions 3 and 4. For V-Codes and E-codes, the implied decimal is between positions 4 and 5. For inapplicable 4th or 5th digits, a dash is inserted. For procedure codes, there is an implied decimal between positions 2 and 3. For inapplicable 3rd or 4th digits, a dash is inserted.

APPENDIX A

Definition of  Terms

Hospitals-Short-stay hospitals or hospitals whose specialty is general (medical or surgical), or children's general. Hospitals must have 6 beds or more staffed for patients use. Federal hospitals and hospital units of institutions are not included.

Free-Standing Ambulatory Surgery Centers-Facilities listed in the 1993 Freestanding Outpatient Surgery Center Database and Medicare-certified facilities included in the HCFA Provider-of-Services (POS) file. Facilities specializing in dentistry, podiatry, abortion, family planning, or birthing are excluded.

Ambulatory Surgery-Scheduled outpatient surgery performed in any of the following locations: general or main operating room, satelitte operating room, cystoscopy room, endoscopy room, cardiac catherterization lab, laser procedures room.

First-listed diagnosis-The coded diagnosis which is listed first on the face sheet of the medical record. The number of first-listed diagnoses is equivalent to the number of ambulatory surgery visits.

Procedures-Surgical or nonsurgical operations, procedures, or special treatments listed by the physician on the medical record. In the NSAS, all terms listed on the face sheet (summary sheet) of the medical record under the caption "operation," "operative procedures," "operations and/or special treatment," and the like are transcribed in the order listed. A maximum of six procedures is coded.

Rate of procedures-The ratio of the number of procedures during a year to the number of persons in the civilian population on July 1 of that year.

Age-The age of the patient on the birthday prior to the date of surgery.

Population-Civilian population is the resident population excluding members of the Armed Forces.

Geographic region-Hospitals are classified by location in one of the four geographic regions of the United States corresponding to those used by the U.S. Bureau of the Census:

Geographic Region States included

Northeast.............Maine, New Hampshire, Vermont
                            Massachusetts, Rhode Island,
                            Connecticut, New York, New Jersey,
                            and Pennsylvania

Midwest..............Michigan, Ohio, Illinois, Indiana,
                           Wisconsin, Minnesota, Iowa,
                           Missouri, North Dakota,
                           South Dakota, Nebraska,
                           and Kansas

South..................Delaware, Maryland, District of Columbia,
                           Virginia, West Virginia, North Carolina,
                           South Carolina, Georgia, Florida, Kentucky,
                           Tennessee, Alabama, Mississippi, Arkansas,
                           Louisiana, Oklahoma, and Texas

West...................Montana, Idaho, Wyoming, Colorado,
                           New Mexico, Arizona, Utah, Nevada, Washington,
                           Oregon, California, Hawaii, and Alaska

APPENDIX B

The International Classification of Diseases, 9th Revision, Clinical Modification, which has been used for coding NHDS data since 1979, undergoes annual updating. Assignment of new diagnostic and procedure codes, fourth and fifth digit expansion of codes, as well as code deletions, are contained in addenda developed by the ICD-9-CM Coordination and Maintenance Committee and approved by the Director of NCHS and the Administrator of the Health Care Financing Administration. Addenda to the ICD-9-CM become effective on October 1 of the calendar year and have been released for 1986 through 1995.

As described earlier in this document, the 1995 NSAS involved two data collection modes: manual and abstract service. All data collected manually were coded using the third edition of the ICD-9-CM, which includes the addenda for 1986 through 1994. Data collected via abstract service were coded using two different ICD-9-CM revisions. For the first 9 months of 1995, the ICD-9-CM including the addendum of October 1, 1986-94 was used; for the last 3 months the October 1995 addendum was used. Therefore, data provided by automated systems for the last three months of 1995 was converted back to the code assignment under the October 1994 addendum. This was done in order to prevent NHDS data users from mistaking partial year estimates for annual estimates.

In order to assist users in data retrieval, a conversion table is provided that shows the date of introduction of each new code and the previously assigned code equivalent, which had been used for reporting the selected diagnosis or procedure prior to issuance of the new code.

DIAGNOSES CODES
Current code(s) assignment	Effective October 1	Previous code(s) assignment
008.00-008.09	1992	008.0
008.43-008.47	1992	008.49
008.61-008.69	1992	008.6
041.00-041.09	1992	041.0
041.10-041.19	1992	041.1
041.81-041.89	1992	041.8
042	1994	042.0-042.2,042.9,043.0-043.3, 043.9,044.0,044.9
042.0-042.9	1986	279.19
043.0-043.9	1986	279.19
044.0-044.9	1986	279.19
070.20-070.21	1991	070.2
070.22	1994	070.20
070.23	1994	070.21
070.30-070.31	1991	070.3
070.32	1994	070.30
070.33	1994	070.31
070.41-070.49	1991	070.4
070.44	1994	070.41
070.51-070.59	1991	070.5
070.54	1994	070.51
077.98-077.99	1993	077.9
078.10-078.11,078.19	1993	078.1
078.88	1993	078.89
079.4	1993	079.8
079.50-079.53,079.59	1993	079.8
079.88-079.89	1993	079.8
079.98-079.99	1993	079.9
088.81,088.89	1989	088.8
088.82	1993	088.89
099.40-099.49	1992	099.4
099.50-099.59	1992	078.89
112.84-112.85	1992	112.89
114.4-114.5	1993	114.3
176.0-176.9	1991	173.0-173.9
203.00	1991	203.0
203.01	1991	V10.79
203.10	1991	203.1
203.11	1991	V10.79
203.80	1991	203.8
203.81	1991	V10.79
204.00	1991	204.0
204.01	1991	V10.61
204.10	1991	204.1
204.11	1991	V10.61
204.20	1991	204.2
204.21	1991	V10.61
204.80	1991	204.8
204.81	1991	V10.61
204.90	1991	204.9
204.91	1991	V10.61
205.00	1991	205.0
205.01	1991	V10.62
205.10	1991	205.1
205.11	1991	V10.62
205.20	1991	205.2
205.21	1991	V10.62
205.30	1991	205.3
205.31	1991	V10.62
205.80	1991	205.8
205.81	1991	V10.62
205.90	1991	205.9
205.91	1991	V10.62
206.00	1991	206.0
206.01	1991	V10.63
206.10	1991	206.1
206.11	1991	V10.63
206.20	1991	206.2
206.21	1991	V10.63
206.80	1991	206.8
206.81	1991	V10.63
206.90	1991	206.9
206.91	1991	V10.63
207.00	1991	207.0
207.01	1991	V10.69
207.10	1991	207.1
207.11	1991	V10.69
207.20	1991	207.2
207.21	1991	V10.69
207.80	1991	207.8
207.81	1991	V10.69
208.00	1991	208.0
208.01	1991	V10.60
208.10	1991	208.1
208.11	1991	V10.60
208.20	1991	208.2
208.21	1991	V10.60
208.80	1991	208.8
208.81	1991	V10.60
208.90	1991	208.9
208.91	1991	V10.60
237.70-237.72	1990	237.7
250.02	1993	250.90
250.03	1993	250.91
250.12	1993	250.10
250.13	1993	250.11
250.22	1993	250.20
250.23	1993	250.21
250.32	1993	250.30
250.33	1993	250.31
250.42	1993	250.40
250.43	1993	250.41
250.52	1993	250.50
250.53	1993	250.51
250.62	1993	250.60
250.63	1993	250.61
250.72	1993	250.70
250.73	1993	250.71
250.82	1993	250.80
250.83	1993	250.81
250.92	1993	250.90
250.93	1993	250.91
283.10-283.11,283.19	1993	283.1
305.1	1994	305.10,305.11,305.12,
		305.13 (delete code)
320.81-320.89	1992	320.8
312.81-312.82,381.89	1994	312.8
333.92-333.93	1994	333.99
337.20-337.22,337.29	1993	337.5
342.00-342.02	1994	342.0
342.10-342.12	1994	342.1
342.80-342.82	1994	342.9
342.90-342.92	1994	342.9
344.00-344.04,344.09	1994	344.0
344.30-344.32	1994	344.3
344.40-344.42	1994	344.4
344.81-344.89	1993	344.8
345.00-345.01	1989	345.0
345.10-345.11	1989	345.1
345.40-345.41	1989	345.4
345.50-345.51	1989	345.5
345.60-345.61	1989	345.6
345.70-345.71	1989	345.7
345.80-345.81	1989	345.8
345.90-345.91	1989	345.9
346.00-346.01	1992	346.0
346.10-346.11	1992	346.1
346.20-346.21	1992	346.2
346.80-346.81	1992	346.8
346.90-346.91	1992	346.9
355.71	1993	354.4
355.79	1993	355.7
371.82	1992	371.89
374.87	1990	374.89
403.00-403.01	1989	403.0
403.10-403.11	1989	403.1
403.90-403.91	1989	403.9
404.00-404.03	1989	404.0
404.10-404.13	1989	404.1
404.90-404.93	1989	404.9
410.00-410.02	1989	410.0
410.10-410.12	1989	410.1
410.20-410.22	1989	410.2
410.30-410.32	1989	410.3
410.40-410.42	1989	410.4
410.50-410.52	1989	410.5
410.60-410.62	1989	410.6
410.70-410.72	1989	410.7
410.80-410.82	1989	410.8
410.90-410.92	1989	410.9
411.81	1989	410.9
411.89	1989	411.8
414.00-414.01	1994	414.0
414.02-414.03	1994	996.03
429.71	1989	410.0-410.9
429.79	1989	410.0-410.9
433.00-433.01	1993	433.0
433.10-433.11	1993	433.1
433.20-433.21	1993	433.2
433.30-433.31	1993	433.3
433.80-433.81	1993	433.8
433.90-433.91	1993	433.9
434.00-434.01	1993	434.0
434.10-434.11	1993	434.1
434.90-434.91	1993	434.9
437.7	1992	780.9
440.20-440.22	1992	440.2
440.23	1993	440.20 & 707.1 or 707.8 or 707.9
440.24	1993	440.20 & 785.4
440.29	1993	440.20
440.30-440.32	1994	996.1
441.00-441.03	1994	441.0
441.6	1993	441.1 & 441.3
441.7	1993	441.2 & 441.4
446.20-446.21,446.29	1990	446.2
451.82-451.84	1993	451.89
482.30-482.39	1992	482.3
482.81-482.89	1992	482.8
483.0	1992	483
483.8	1992	483
491.20-491.21	1991	491.2
493.20	1989	493.90
493.21	1989	493.91
512.1	1994	997.3
518.81	1987	799.1
518.82-518.89	1987	518.8
524.00-524.09	1992	524.0
524.10-524.19	1992	524.1
524.60-524.69	1991	524.6
524.70-524.79	1992	524.8
530.10-530.11, 530.19	1993	530.1
530.81	1993	530.1
530.82-530.84, 530.89	1993	530.8
535.00-535.01	1991	535.0
535.10-535.11	1991	535.1
535.20-535.21	1991	535.2
535.30-535.31	1991	535.3
535.40-535.41	1991	535.4
535.50-535.51	1991	535.5
535.60-535.61	1991	535.6
536.3	1994	536.8
537.82	1990	537.89
537.83	1991	537.82
556.0-556.6	1994	556
556.8-556.9	1994	556
562.02	1991	562.00
562.03	1991	562.01
562.12	1991	562.10
562.13	1991	562.11
569.84	1990	557.1
569.85	1991	569.84
593.70-593.73	1994	593.7
596.51-596.53	1992	596.5
596.54	1992	344.61
596.55-596.59	1992	596.5
599.81-599.89	1992	599.8
645.0	1991	645
651.30-651.31,651.33	1989	651.00-651.01,651.03
651.40-651.41,651.43	1989	651.10-651.11,651.13
651.50-651.51,651.53	1989	651.20-651.21,651.23
651.60-651.61,651.63	1989	651.80-651.81,651.83
654.20-654.21,654.23	1990	654.2,654.9
654.90-654.94	1990	654.2,654.9
657.0	1991	657
659.60,659.61,659.63	1992	659.80,659.81,659.83
665.10,665.11	1992	665.10,665.11,665.12,665.14
Note: The title for the subcategory, 665.1 has been changed,  making the fifth-digit subclassification, 665.12 and 665.14 invalid.
670.0	1991	670
672.0	1991	672
677	1994	* No previous code assignments.
692.72-692.74	1992	692.79
692.82-692.83	1992	692.89
702.0-702.8	1991	702
702.11,702.19	1994	702.1
704.02	1993	704.09
709.00-709.01,709.09	1994	709.0
710.5	1992	288.3,729.1
733.10-733.16, 733.19	1993	733.1
738.10-738.19	1992	738.1
747.60-747.64, 747.69	1993	747.6
747.82	1993	747.89
753.10-753.17,753.19	1990	753.1
759.81-759.89	1989	759.8
759.83	1994	759.89
760.75	1991	760.79
760.76	1994	760.79
764.00-764.09	1988	764.0
764.10-764.19	1988	764.1
764.20-764.29	1988	764.2
764.90-764.99	1988	764.9
765.00-765.09	1988	765.0
765.10-765.19	1988	765.1
780.01-780.09	1992	780.0
780.03	1993	780.01
780.57	1992	780.51,780.53
781.8	1994	781.9
787.01-787.03	1994	787.0
788.20-788.21, 788.29	1993	788.2
788.30-788.39	1992	788.3
788.40-788.43	1993	788.4
788.61-788.62, 788.69	1993	788.6
789.00-789.07, 789.09	1994	789.0
789.30-789.37, 789.39	1994	789.3
789.40-789.47, 789.49	1994	789.4
789.60-789.67, 789.69	1994	789.6
790.91	1993	790.9
790.92	1993	286.9
790.93, 790.99	1993	790.9
795.71	1994	795.8 (delete code)
795.79	1994	795.7
795.8	1986	795.7
864.05	1992	864.09
864.15	1992	864.19
909.5	1994	909.9
925.1-925.2	1993	925
995.60-995.69	1993	995.0
996.04	1994	996.09
996.51-996.59	1987	996.5
996.60-996.69	1989	996.6
996.70-996.79	1989	996.7
996.80-996.89	1987	996.8
996.85	1990	999.8
998.81-998.82, 998.89	1994	998.8
V03.81-V03.82, V03.89	1994	V03.8
V05.3-V05.4	1993	V05.8
V06.5-V06.6	1994	V06.8
V07.31,V07.39	1994	V07.3
V07.4	1992	V07.8
V08	1994	044.9, 795.8 (delete code)
V09.0-V09.91	1993	* No previous code assignments
V12.00-V12.03, V12.09	1994	V12.0
V12.70-V12.72, V12.79	1994	V12.7
V13.00-V13.01, V13.09	1994	V13.0
V15.82	1994	305.13 (delete code)
V25.43	1992	V25.49
V25.5	1992	V25.8
V29.0-V29.8	1992	V71.8
V29.9	1992	V71.9
V30.00-V30.01	1989	V30.0
V31.00-V31.01	1989	V31.0
V32.00-V32.01	1989	V32.0
V33.00-V33.01	1989	V33.0
V34.00-V34.01	1989	V34.0
V35.00-V35.01	1989	V35.0
V36.00-V36.01	1989	V36.0
V37.00-V37.01	1989	V37.0
V39.00-V39.0l	1989	V39.0
V43.60-V43.66, V43.69	1994	V43.6
V45.00	1994	V45.89
V45.01	1994	V45.0
V45.02, V45.09	1994	V45.89
V45.51	1994	V45.5
V45.52, V45.59	1994	V45.89
V45.82	1994	V45.89
V49.60-V49.67	1994	V49.5
V49.70-V49.77	1994	V49.5
V50.41-V50.42, V50.49	1994	V50.8
V53.31	1994	V53.3
V53.32, V53.39	1994	V53.9
V57.21-V57.22	1994	V57.2
V58.41, V58.49	1994	V58.4
V58.81, V58.89	1994	V58.8
V65.40-V65.45, V65.49	1994	V65.4
V69.0-V69.3	1994	* No previous code assignments.
V69.8-V69.9	1994	* No previous code assignments.
V72.81-V72.85	1993	V72.8
V73.88-V73.89	1993	V73.8
V73.98-V73.99	1993	V73.9
E869.4	1994	E869.8

PROCEDURE   CODES
Current code(s) assignment	Effective October 1	Previous code(s) assignment
02.96	1992	89.19
03.90	1987	03.99 (Insertion of Catheter)
11.75	1989	11.79
11.76	1989	11.62
20.96-20.98	1986	20.95
22.12	1988	22.11
26.12	1988	26.11
29.31	1991	83.02
29.32	1991	29.3
29.33	1991	29.3
29.39	1991	29.3
31.45	1988	31.43-31.44
31.95	1989	31.75
32.01	1989	32.0
32.09	1989	32.0
32.28	1989	32.29
33.27	1987	33.22 + 33.27
33.28	1987	33.27
33.29	1987	33.28-33.29
33.6	1990	33.5 + 37.5
34.05	1994	34.99
35.84	1988	35.82
35.96	1986	35.03
36.00-36.03	1986	36.0
36.04	1986	39.97
36.05	1987	36.01
36.05	1986	36.01 (Before October 1986 contents of current code 36.05 would have been assigned to 36.0), 36.02
36.09	1986	36.0
36.09	1991	36.00 (Code Deleted)
37.26-37.27	1988	37.29
37.34	1988	37.33
37.70 (Leads only)	1987 (Leads/Device)	37.70
37.71-37.72 (Leads only)	1987 (Leads/Device)	37.74
37.73 (Leads only)	1987 (Leads/Device)	37.73
37.74 (Leads only)	1987 (Leads/Device)	37.76
37.75 (Leads only)	1987 (Leads/Device)	37.89
37.76 (Leads only)	1987 (Leads/Device)	37.81
37.77 (Leads only)	1987 (Leads/Device)	37.83-37.84
37.78	1987	37.71-37.72
37.79	1987	86.09
37.80-37.87	1992	89.49 (Code deleted, this procedure is included in the code for pacemaker insertion/replacement)
37.80 (Device only)	1987 (Leads/Device)	37.73-37.77
37.81 (Device only)	1987 (Leads/Device)	37.73-37.77
37.82 (Device only)	1987 (Leads/Device)	37.73-37.77
37.83 (Device only)	1987 (Leads/Device)	37.73-37.77
37.85-37.87	1987	37.85
37.89	1987	37.86 + 37.89
37.94-37.98	1986	37.99
38.22	1986	38.29
38.44 (Abdominal Aorta only)	1986	38.44 (Entire Aorta)
38.45 (Thoracic Aorta only)	1986	38.44-38.45
38.95	1989	38.93
39.28	1991	39.29
39.65	1988	39.61
39.66	1990	39.65
41.00-41.03	1988	41.0
41.04	1994	99.79
42.25	1988	42.24
42.33	1989	42.32, 42.39
42.33	1990	42.91
43.11	1989	43.1
43.19	1989	43.1, 43.2
43.41	1989	43.41,43.49
44.21	1986	44.2
44.22	1986	44.99
44.29	1986	44.2
44.43	1989	43.49,45.32
44.44	1989	38.86
44.49	1989	43.0
44.93-44.94	1986	44.99
45.16	1988	45.14 (45.15 before 1987)
45.30	1989	45.31,45.32
45.42	1988	45.41
45.43	1989	45.49
45.75 (Hartmann Resection Added)	1988	48.66 (Code Deleted)
45.95	1987	45.93
46.13	1992	46.12 (Code Deleted)
46.32	1989	46.39
46.85	1989	46.99
49.31	1989	49.3
49.39	1989	49.3
51.10	1989	51.97
51.11	1989	51.11,51.97
51.14	1989	51.12
51.15	1989	51.97
51.22	1991	51.21 (Code Deleted),51.22
51.23	1991	51.22
51.64	1989	51.69
51.84-51.88	1989	51.97
51.97	1986	52.91,51.99, or 51.82
51.98	1986	51.99
52.13	1989	51.97,52.91
52.14	1989	52.11
52.21	1989	52.2
52.22	1989	52.2
52.93	1989	52.93 + 52.91
52.94	1989	52.09
52.97	1989	52.91
52.98	1989	52.91
52.99	1989	52.93,52.94,52.99
54.24	1987	54.23
54.25	1993	54.98
55.03-55.04	1986	55.02
56.33-56.34	1987	56.33
56.35	1987	45.12
57.17-57.18	1989	57.21
57.22	1989	57.22,57.82
58.31	1990	58.3
58.39	1990	58.3
58.93	1986	57.99
59.96	1986	59.95
60.95	1991	60.99
64.97	1986	64.95
66.01	1992	66.0
66.02	1992	66.73
68.15	1987	68.14
68.16	1987	68.13
68.9	1992	68.4
74.3	1992	69.11 (Code Deleted)
77.56	1989	77.89,78.49,81.18
77.57	1989	77.89,80.48,81.18,83.85
77.58	1989	77.59,81.18
78.10	1991	78.40
78.11	1991	78.41
78.12	1991	78.42
78.13	1991	78.43
78.14	1991	78.44
78.15	1991	78.45
78.16	1991	78.46
78.17	1991	78.47
78.18	1991	78.48
78.19	1991	78.49
78.20	1991	78.10,78.20,78.30
78.21	1991	78.11,78.31
78.22	1991	78.12,78.22,78.32
78.23	1991	78.13,78.23,78.33
78.24	1991	78.14,78.34
78.25	1991	78.15,78.25,78.35
78.27	1991	78.17,78.27,78.37
78.28	1991	78.18,78.38
78.29	1991	78.11,78.16,78.19,78.29,78.39
78.39	1991	78.31
78.90 2/	1987	78.40
78.91 2/	1987	78.41
78.92 2/	1987	78.42
78.93 2/	1987	78.43
78.94 2/	1987	78.44
78.95 2/	1987	78.45
78.96 2/	1987	78.46
78.97 2/	1987	78.47
78.98 2/	1987	78.48
78.99 2/	1987	78.49
80.50-80.59	1986	80.5
81.03	1989	81.02
81.04-81.05	1989	81.03,81.04,81.05
81.06-81.07	1989	81.06,81.07
81.08	1989	81.06,81.07,81.08
81.09	1989	81.08
81.40	1989	81.69
81.51	1989	81.51,81.59
81.52	1989	81.61,81.62,81.63,81.64
81.53	1989	81.51,81.59,81.61,81.62, 81.63, 81.64
81.54-81.55	1989	81.41
81.56	1989	81.48
81.57	1989	81.31,81.39
81.59	1989	81.39
81.72	1989	81.79
81.73-81.74	1989	81.86
81.75	1989	81.87
81.79	1989	81.79,81.87
81.80	1989	81.81
81.97	1992	81.59
85.95	1987	85.99
85.96	1987	85.99
86.06	1987	86.09
86.07	1990	86.09
86.27	1986	86.22-86.23
86.28	1988	86.22
86.93	1987	86.89
88.90	1986	88.39
88.91	1986	89.15
88.92	1986	89.39
88.93	1986	89.15
88.94	1986	89.39
88.95	1986	89.29
88.97	1989	88.99
88.98	1989	88.90
88.99	1986	89.39
89.10	1989	89.15
89.17-89.18	1988	89.15
89.19	1989	89.15
89.50	1991	89.54
93.90	1988	93.92
94.61-94.69	1989	94.25
96.6	1986	96.35
96.70	1991	93.92 (Code Deleted)
96.71	1991	93.92 (Code Deleted)
96.72	1991	93.92 (Code Deleted)
97.05	1989	51.97
98.51-98.52	1989	59.96 (Code Deleted)
98.59	1989	59.96 (Code Deleted)
99.15	1986	99.29
99.28	1994	99.25
99.71-99.79 3/	1988	99.07
99.85	1987	93.35
99.86	1987	93.39
99.88	1988	99.83

1/ Before October 1986 contents of current code 36.05 would have been assigned to 36.0.

2/ Codes 78.90-78.99 were retitled as "Insertion of bone growth stimulator" in October 1987; the previous contents of codes 78.90-78.99 were reassigned to codes 78.40-78.49.

3/ Codes 99.71-99.79 were deleted in October 1987; their contents were not transferred elsewhere. In the October 1988 revision, codes 99.71-99.79 were reclassified as "Therapeutic apheresis."

APPENDIX C

Civilian Population* by Sex, Age, Geographic Region and Race United States, July 1, 1995

[Population estimates consistent with Series P-25,  Current Population Reports, U.S. Bureau of the Census]

Age, geographic region and race
	Both sexes	Male	Female
	Population in thousands
All ages	261,407	127,134	134,273
Northeast	51,395	24,751	26,644
Midwest	61,698	30,003	31,695
South	91,143	44,018	47,125
West	57,170	28,361	28,809
White	217,041	106,062	110,979
Black	32,883	15,513	17,370
All other	11,483	5,559	5,924
Under 15 years	57,726	29,554	28,172
Under 1 year	3,848	1,970	1,878
1-4 years	15,743	8,055	7,688
5-14 years	38,134	19,529	18,606
Northeast	10,646	5,452	5,193
Midwest	13,491	6,910	6,581
South	20,027	10,243	9,784
West	13,562	6,948	6,614
White	45,728	23,463	22,264
Black	9,002	4,565	4,437
All other	2,996	1,526	1,470
15-44 years	117,976	58,700	59,276
15-24 years	35,431	17,909	17,522
25-34 years	40,349	19,972	20,377
35-44 years	42,195	20,819	21,377
Northeast	22,896	11,354	11,542
Midwest	27,770	13,835	13,935
South	40,999	20,177	20,823
West	26,311	13,335	12,976
White	96,442	48,412	48,030
Black	15,803	7,506	8,297
All other	5,731	2,782	2,949
45-64 years	52,173	25,192	26,981
45-54 years	31,043	15,149	15,894
55-64 years	21,130	10,043	11,087
Northeast	10,561	5,045	5,516
Midwest	12,344	5,985	6,359
South	18,434	8,837	9,597
West	10,834	5,325	5,509
White	44,817	21,874	22,943
Black	5,358	2,388	2,971
All other	1,998	930	1,068
65 years & over	33,532	13,689	19,844
65-74 years	18,759	8,342	10,417
75-84 years	11,145	4,330	6,815
85 years and over	3,628	1,017	2,611
Northeast	7,293	2,900	4,393
Midwest	8,094	3,273	4,821
South	11,683	4,762	6,921
West	6,462	2,753	3,709
White	30,055	12,313	17,742
Black	2,719	1,055	1,665
All other	758	321	437

*The NHDS used the civilian noninstitutional population to calculate hospital utilization rates from 1965 through 1980. Beginning in 1981, the civilian resident population has been used to calculate rates. If you have purchased NHDS tapes for years before 1981 and calculated rates using the civilian noninstitutionalized population provided in the documentation, these rates will have to be adjusted to be comparable to 1995 rates using the civilian resident population.

Civilian Population of the United States, July 1, 1995. Estimates by Age, Sex, and Region.

Data are consistent with the estimates announced in Census Advisory CB94-43. Methodology is described in
Current Population Report Series P25-1106. Release date 3/15/94

                                                                            Civilian population in thousands

	United States			Northeast			Midwest			South			West
AGE	TOTAL	MALE	FEMALE	TOTAL	MALE	FEMALE	TOTAL	MALE	FEMALE	TOTAL	MALE	FEMALE	TOTAL	MALE	FEMALE
ALL	261,407	127,134	134,273	51,395	24,751	26,644	61,698	30,003	31,695	91,143	44,018	47,125	57,170	28,361	28,809
0-4	19,591	10,025	9,566	3,617	1,852	1,765	4,393	2,248	2,145	6,782	3,469	3,314	4,799	2,456	2,342
5-9	19,220	9,843	9,377	3,613	1,853	1,760	4,498	2,305	2,193	6,631	3,390	3,240	4,479	2,295	2,184
10-14	18,915	9,685	9,229	3,416	1,747	1,668	4,601	2,358	2,243	6,614	3,384	3,230	4,285	2,197	2,088
15-19	17,974	9,189	8,785	3,229	1,645	1,583	4,417	2,257	2,160	6,383	3,248	3,134	3,945	2,038	1,908
20-24	17,458	8,720	8,738	3,259	1,627	1,632	4,146	2,070	2,076	6,244	3,066	3,178	3,809	1,957	1,851
25-29	18,721	9,282	9,439	3,733	1,849	1,884	4,267	2,110	2,157	6,457	3,156	3,301	4,264	2,167	2,097
30-34	21,629	10,690	10,938	4,317	2,131	2,186	4,960	2,452	2,508	7,445	3,637	3,808	4,906	2,470	2,436
35-39	22,064	10,906	11,158	4,392	2,167	2,225	5,208	2,588	2,621	7,548	3,685	3,863	4,915	2,466	2,449
40-44	20,132	9,913	10,219	3,967	1,934	2,032	4,771	2,358	2,413	6,922	3,384	3,538	4,472	2,237	2,236
45-49	17,419	8,532	8,887	3,492	1,688	1,804	4,081	2,002	2,079	6,068	2,961	3,108	3,778	1,882	1,896
50-54	13,624	6,617	7,008	2,766	1,328	1,439	3,201	1,557	1,644	4,801	2,318	2,484	2,855	1,414	1,441
55-59	11,084	5,316	5,767	2,239	1,065	1,174	2,655	1,279	1,376	3,949	1,877	2,072	2,241	1,096	1,145
60-64	10,046	4,727	5,320	2,064	965	1,099	2,407	1,147	1,260	3,616	1,681	1,934	1,960	933	1,027
65-69	9,928	4,506	5,422	2,125	951	1,173	2,343	1,072	1,271	3,533	1,594	1,939	1,928	889	1,039
70-74	8,831	3,836	4,995	1,905	811	1,094	2,075	902	1,172	3,109	1,343	1,766	1,742	780	962
75-79	6,681	2,720	3,961	1,466	577	888	1,625	651	974	2,302	937	1,365	1,289	555	734
80-84	4,464	1,609	2,854	984	344	640	1,108	392	716	1,530	548	982	842	326	516
85+	3,628	1,017	2,611	813	217	597	944	256	688	1,209	341	869	662	204	458
0-14	57,726	29,554	28,172	10,646	5,452	5,193	13,491	6,910	6,581	20,027	10,243	9,784	13,562	6,948	6,614
15-44	117,976	58,700	59,276	22,896	11,354	11,542	27,770	13,835	13,935	40,999	20,177	20,823	26,311	13,335	12,976
45-64	52,173	25,192	26,981	10,561	5,045	5,516	12,344	5,985	6,359	18,434	8,837	9,597	10,834	5,325	5,509
15+	203,681	97,581	106,101	40,750	19,299	21,450	48,207	23,093	25,114	71,117	33,776	37,341	43,608	21,413	22,195
45+	85,705	38,881	46,825	17,853	7,945	9,908	20,437	9,258	11,179	30,118	13,599	16,518	17,297	8,078	9,219
65+	33,532	13,689	19,844	7,293	2,900	4,393	8,094	3,273	4,821	11,683	4,762	6,921	6,462	2,753	3,709
75+	14,773	5,347	9,427	3,263	1,138	2,125	3,676	1,299	2,378	5,041	1,825	3,216	2,792	1,084	1,708

Civilian Population of the United States, July 1, 1995. Estimates by Age, Sex, and Race (Consistent with the 1990 Census, as enumerated.)

______________________________________________________________________________________________
                              All Races                               White                                  Black                             Other Races
  Age        Total       Male      Female       Total     Male      Female      Total        Male     Female      Total     Male    Female
______________________________________________________________________________________________
                                                                  Civilian population in thousands

All	261,407	127,134	134,273	217,041	106,062	110,979	32,883	15,513	17,370	11,483	5,559	5,924
0-4	19,591	10,025	9,566	15,451	7,924	7,527	3,100	1,570	1,530	1,040	531	509
0	3,848	1,970	1,878	3,015	1,547	1,467	621	314	307	212	108	104
1	3,840	1,964	1,876	3,028	1,552	1,475	608	307	301	205	105	100
2	3,882	1,990	1,892	3,067	1,575	1,492	611	311	300	204	104	100
3	3,965	2,026	1,939	3,137	1,606	1,531	619	313	305	209	107	103
4	4,056	2,075	1,981	3,205	1,643	1,562	642	325	317	209	107	103
5-9	19,220	9,843	9,377	15,237	7,818	7,418	3,025	1,535	1,491	958	490	468
5	4,039	2,069	1,970	3,198	1,642	1,557	641	325	316	201	103	98
6	3,888	1,991	1,897	3,071	1,575	1,496	625	318	307	192	98	94
7	3,810	1,949	1,861	3,016	1,547	1,470	602	304	298	191	98	93
8	3,616	1,851	1,765	2,876	1,475	1,401	561	285	276	180	92	88
9	3,867	1,983	1,883	3,075	1,580	1,495	597	303	293	195	99	95
10-14	18,915	9,685	9,229	15,040	7,721	7,319	2,877	1,460	1,417	998	505	493
10	3,869	1,985	1,884	3,084	1,586	1,499	588	299	289	197	100	97
11	3,705	1,897	1,808	2,952	1,516	1,436	559	283	276	194	98	95
12	3,778	1,932	1,846	2,998	1,537	1,460	576	292	284	204	103	102
13	3,811	1,949	1,863	3,030	1,553	1,477	580	294	286	202	102	100
14	3,751	1,922	1,829	2,976	1,529	1,447	574	292	283	201	102	99
15-19	17,974	9,189	8,785	14,290	7,328	6,962	2,806	1,418	1,387	878	443	435
15	3,790	1,944	1,846	2,994	1,540	1,454	602	306	296	194	98	96
16	3,627	1,866	1,761	2,877	1,483	1,393	570	291	279	180	91	89
17	3,596	1,852	1,744	2,864	1,479	1,385	556	284	273	176	89	86
18	3,482	1,775	1,708	2,779	1,421	1,358	544	273	271	160	80	79
19	3,479	1,753	1,726	2,777	1,405	1,372	533	264	269	168	84	85
20-24	17,458	8,720	8,738	13,982	7,027	6,955	2,562	1,239	1,322	914	453	461
20	3,477	1,746	1,731	2,786	1,406	1,381	523	257	265	168	83	84
21	3,327	1,666	1,661	2,652	1,334	1,318	501	245	256	174	87	88
22	3,314	1,654	1,660	2,645	1,330	1,316	491	237	254	178	88	90
23	3,493	1,742	1,752	2,797	1,404	1,392	509	244	265	187	93	95
24	3,846	1,911	1,935	3,101	1,553	1,548	538	256	282	207	103	105
25-29	18,721	9,282	9,439	15,186	7,603	7,583	2,536	1,193	1,343	999	486	513
25	3,810	1,894	1,916	3,090	1,549	1,541	514	243	270	207	102	104
26	3,689	1,828	1,861	3,002	1,501	1,501	487	230	257	200	97	103
27	3,663	1,818	1,846	2,967	1,488	1,479	498	234	264	198	96	102
28	3,543	1,752	1,791	2,889	1,443	1,445	472	221	251	182	87	95
29	4,015	1,991	2,025	3,238	1,622	1,616	565	265	299	213	104	109
30-34	21,629	10,690	10,938	17,803	8,898	8,905	2,776	1,285	1,491	1,050	508	542
30	4,161	2,056	2,105	3,397	1,697	1,700	556	258	298	207	100	107
31	4,220	2,085	2,136	3,464	1,730	1,734	547	254	293	210	101	109
32	4,310	2,130	2,181	3,547	1,771	1,776	549	254	295	214	104	110
33	4,380	2,159	2,221	3,628	1,809	1,819	550	253	297	202	97	105
34	4,557	2,261	2,296	3,766	1,890	1,876	574	265	308	217	105	112
35-39	22,064	10,906	11,158	18,319	9,156	9,163	2,749	1,275	1,474	996	476	520
35	4,551	2,255	2,296	3,764	1,885	1,879	576	268	308	211	102	110
36	4,391	2,167	2,224	3,650	1,823	1,828	544	251	294	197	94	103
37	4,451	2,198	2,253	3,699	1,847	1,852	552	255	296	200	96	104
38	4,185	2,064	2,121	3,490	1,740	1,750	513	237	275	182	87	96
39	4,485	2,222	2,263	3,716	1,861	1,855	564	263	301	205	97	108
40-44	20,132	9,913	10,219	16,863	8,400	8,462	2,375	1,096	1,279	894	417	478
40	4,318	2,133	2,186	3,595	1,796	1,799	528	245	284	195	92	103
41	4,110	2,021	2,090	3,440	1,711	1,729	486	224	262	184	86	98
42	3,987	1,961	2,026	3,351	1,666	1,684	459	211	248	178	83	95
43	3,870	1,897	1,973	3,246	1,611	1,635	449	206	244	175	80	94
44	3,846	1,902	1,944	3,231	1,616	1,615	452	210	242	163	76	87
45-49	17,419	8,532	8,887	14,833	7,347	7,486	1,852	844	1,008	734	342	393
45	3,732	1,836	1,896	3,137	1,562	1,575	432	199	233	163	75	88
46	3,550	1,739	1,811	3,012	1,493	1,519	387	176	211	151	70	82
47	3,580	1,749	1,830	3,039	1,502	1,536	387	175	211	154	72	83
48	3,653	1,787	1,866	3,187	1,575	1,612	334	151	183	132	61	70
49	2,904	1,421	1,484	2,458	1,215	1,243	312	142	170	134	64	70
50-54	13,624	6,617	7,008	11,720	5,750	5,971	1,381	619	761	523	248	276
50	2,888	1,407	1,481	2,465	1,214	1,251	302	136	166	121	57	64
51	2,781	1,352	1,429	2,393	1,175	1,218	280	126	154	108	51	57
52	2,913	1,417	1,496	2,536	1,245	1,291	274	123	151	103	48	54
53	2,567	1,243	1,324	2,205	1,079	1,126	267	119	148	95	45	50
54	2,476	1,197	1,278	2,121	1,037	1,084	258	115	143	97	46	51
55-59	11,084	5,316	5,767	9,540	4,625	4,915	1,138	500	638	406	192	214
55	2,312	1,113	1,199	1,967	956	1,011	254	114	141	91	43	48
56	2,315	1,112	1,203	1,996	970	1,026	236	103	134	83	40	43
57	2,291	1,099	1,192	1,969	954	1,015	239	105	133	83	39	44
58	2,029	970	1,058	1,763	852	911	195	85	110	71	33	38
59	2,137	1,023	1,115	1,845	893	952	214	94	120	78	37	42
60-64	10,046	4,727	5,320	8,723	4,152	4,571	988	425	563	334	149	185
60	2,111	997	1,114	1,832	875	958	206	89	118	72	33	39
61	1,934	918	1,016	1,678	806	873	189	82	107	67	30	37
62	1,939	912	1,027	1,672	796	876	199	86	113	68	30	38
63	1,968	926	1,042	1,717	818	899	188	81	108	62	27	35
64	2,095	975	1,120	1,823	858	965	205	88	117	66	29	37
65-69	9,928	4,506	5,422	8,726	3,993	4,733	920	393	527	282	119	162
65	2,067	959	1,108	1,799	844	954	205	87	118	63	27	36
66	2,010	923	1,087	1,761	814	947	192	84	107	58	24	33
67	2,041	930	1,110	1,796	827	968	189	80	109	56	23	32
68	1,913	856	1,056	1,691	762	929	169	72	97	52	22	30
69	1,897	837	1,060	1,679	745	934	165	70	96	52	22	30
70-74	8,831	3,836	4,995	7,918	3,462	4,456	697	280	416	216	94	122
70	1,884	829	1,055	1,677	743	934	157	64	93	49	21	28
71	1,822	797	1,025	1,634	720	914	143	57	86	45	20	25
72	1,762	769	993	1,578	693	885	138	56	82	46	20	26
73	1,712	736	976	1,543	667	875	130	52	78	39	17	22
74	1,652	705	947	1,487	638	848	129	51	78	37	16	21
75-79	6,681	2,720	3,961	6,039	2,470	3,569	510	194	316	132	56	77
75	1,512	635	877	1,358	573	785	122	49	73	32	14	19
76	1,405	583	821	1,272	530	741	105	42	63	28	11	16
77	1,312	532	780	1,189	485	704	97	37	61	25	11	15
78	1,264	504	760	1,146	460	686	94	34	60	24	10	14
79	1,189	466	723	1,074	422	652	91	34	58	23	10	13
80-84	4,464	1,609	2,854	4,069	1,469	2,600	318	107	211	76	33	44
80	1,076	409	668	981	374	607	76	26	50	19	8	11
81	976	361	616	890	330	560	70	24	46	16	7	9
82	895	321	574	815	293	522	65	22	43	15	6	9
83	801	280	521	734	256	478	54	18	35	13	6	8
84	715	239	476	649	216	433	54	17	37	12	5	7
85+	3,628	1,017	2,611	3,303	919	2,385	274	79	195	51	19	32
0-14	57,726	29,554	28,172	45,728	23,463	22,264	9,002	4,565	4,437	2,996	1,526	1,470
15-44	117,976	58,700	59,276	96,442	48,412	48,030	15,803	7,506	8,297	5,731	2,782	2,949
45-64	52,173	25,192	26,981	44,817	21,874	22,943	5,358	2,388	2,971	1,998	930	1,068
15+	203,681	97,581	106,101	171,314	82,599	88,715	23,881	10,949	12,932	8,487	4,033	4,454
45+	85,705	38,881	46,825	74,872	34,187	40,685	8,078	3,443	4,635	2,756	1,251	1,504
65+	33,532	13,689	19,844	30,055	12,313	17,742	2,719	1,055	1,665	758	321	437
75+	14,773	5,347	9,427	13,411	4,858	8,553	1,102	381	721	260	107	152

APPENDIX D

Unweighted and Weighted Estimates For Selected NSAS Variables 

                                               UNWEIGHTED N       WEIGHTED ESTIMATE

YEAR OF SURGERY 
95                                                    121,564                         19,959,255

FACILITY TYPE
1                                                        73,995                          16,726,675
2                                                          7,569                            3,232,580

AGEUNITS
1                                                      119,938                          19,788,501
2                                                          1,567                               160,458
3                                                               59                                 10,296

AGEFLAG
1                                                             815                               122,712
2                                                      120,749                          19,836,543

SEX
1                                                        52,746                            8,674,346
2                                                        68,818                          11,284,909

SEXFLAG
1                                                          1,274                               143,213
2                                                      120,290                          19,816,042

RACE
1                                                        61,911                          11,955,685
2                                                          6,007                            1,082,836
3                                                             223                                 48,042
4                                                          1,611                               186,576
5                                                          1,205                               136,397
9                                                        50,607                            6,549,719

STATUS AT DISPOSITION
1                                                      110,390                          17,871,611
2                                                          2,903                               648,098
3                                                          1,637                               210,314
4                                                          1,430                               320,946
5                                                             160                                 26,768
6                                                             828                               148,756
9                                                          4,216                               732,762

MONTH OF SURGERY
01                                                        9,899                            1,629,814
02                                                        9,473                            1,571,370
03                                                      10,993                            1,809,082
04                                                        9,621                            1,556,813
05                                                      10,725                            1,730,103
06                                                      10,799                            1,797,695
07                                                        9,386                            1,512,699
08                                                      10,948                            1,767,936
09                                                        9,587                            1,584,050
10                                                      10,283                            1,704,943
11                                                      10,448                            1,714,100
12                                                        9,402                            1,580,650

REGION
1                                                        25,562                            4,506,940
2                                                        27,687                            4,994,613
3                                                        44,263                            6,782,334
4                                                        24,052                            3,675,368

                                              UNWEIGHTED N                WEIGHTED ESTIMATE

PRINCIPAL EXPECTED SOURCE OF PAYMENT
00                                                           760                                         88,614
01                                                        2,867                                       461,431
02                                                      38,690                                    6,122,975
03                                                        8,640                                    1,227,583
04                                                           566                                         82,048
05                                                          984                                        151,321
06                                                     13,819                                     2,514,622
07                                                     17,110                                     3,109,001
08                                                     26,346                                     4,107,608
09                                                       3,416                                        470,899
10                                                       1,845                                        408,417
12                                                       6,521                                     1,214,736

OTHER EXPECTED SOURCE OF PAYMENT 1
00                                                           64                                             5,845
01                                                           44                                           11,266
02                                                         816                                         147,887
03                                                      4,214                                         585,311
04                                                         257                                           43,466
05                                                         512                                           74,509
06                                                      9,827                                      1,558,267
07                                                      1,488                                         281,773
08                                                    13,521                                      2,073,054
09                                                      3,056                                         366,744
10                                                             9                                             4,044

MISSING                                        87,756                                   14,807,089

OTHER EXPECTED SOURCE OF PAYMENT 2
00                                                           12                                            2,425
02                                                             6                                               429
03                                                           12                                            1,935
04                                                             8                                            1,149
05                                                           49                                            2,105
06                                                           71                                          10,489
07                                                           27                                           7,426
08                                                         191                                         32,744
09                                                         671                                         61,915
10                                                           49                                         15,984

MISSING                                      120,468                                  19,822,654

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