The International Classification of Diseases (ICD)
9th Revision
The 9th Revision of the ICD codes has two forms:
- ICD9-CM (Clinical Modification)
-
The International Classification of Diseases,
9th Revision, Clinical Modification (ICD9-CM)
is based on the official version of the World
Health Organization's 9th Revision,
International Classification of Diseases (ICD9).
ICD-9-CM, Official Guidelines for Coding and Reporting
can be obtained from:
Superintendent of Documents
P.O. Box 37194
Pittsburg, PA 15250-7954
FAX: (202) 512-2250
- ICD9-MORT (Mortality)
- ICD9 is designed for the classification of Morbidity and
Mortality information for statistical purposes, and for the
indexing of hospital records by disease and operations, for data
storage and retrieval. This publication is maintained by the World Health Organization.
A classification of diseases may be defined as a system of
categories to which morbid entities are assigned according to some
established criteria. There are many possible choices for these
criteria. The anatomist, for example, may desire a classification
based on the part of the body affected whereas the pathologist is
primarily interested in the nature of the disease process, the
public health practitioner in aetiology and the clinician in the
particular manifestation requiring his care. In other words there
are many axes of classification and the particular axis selected
will be determined by the interest of the investigator. A
statistical classification of disease and injury will depend,
therefore, upon the use to be made of the statistics to be
compiled.
Because of this conflict of interests, efforts to base a
statistical classification a strictly logical adherence to any one
axis have failed in the past. The various titles will represent a
series of necessary compromises between classifications based on
aetiology, anatomical site, circumstances of onset, etc., as well
as the quality of information available on medical reports.
Adjustments must also be made to meet the varied requirements of
vital statistics offices, hospitals of different types, medical
services of the armed forces, social insurance organizations,
sickness surveys, and numerous other agencies. While no single
classification will fit all the specialized needs, it should
provide a common basis of classification for general statistical
use; that is storage, retrieval and tabulation of data.
A statistical classification of disease must be confined to a
limited number of categories which will encompass the entire range
of morbid conditions. The categories should be chosen so that they
will facilitate the statistical study of disease phenomena. A
specific disease entity should have a separate title in the
classification only when its separation is warranted because the
frequency of its occurrence, or its importance as a morbid
condition, justifies its isolation as a separate category. On the
other hand, many titles in the classification will refer to groups
of separate but usually related morbid conditions. Every disease
or morbid condition, however, must have a definite and appropriate
place as an inclusion in one of the categories of the statistical
classification. A few items of the statistical list will be
residual titles for other and miscellaneous conditions which cannot
be classified under the more specific titles. These miscellaneous
categories should be kept to a minimum.
It is this element of grouping in a statistical classification
that distinguishes it from a nomenclature, a list or catalogue of
approved names for morbid conditions, which must be extensive in
order to accommodate all pathological conditions. The concepts of
classification and nomenclature are, nevertheless, closely relate
din the sense that some classifications (e.g. in zoology) are so
detailed that they become nomenclatures. Such classifications,
however, are generally unsuitable for statistical analysis.
The aims of a statistical classification of disease cannot be
better summarized than in the following paragraphs written by
William Farr (1) a century ago:
"The causes of death were tabulated in the early Bills of
Mortality (Tables Mortuaires) alphabetically; and this course has
the advantage of not raising any of those nice questions in which
it is vain to expect physicians and statisticians to agree
unanimously. But statistics is eminently a science of
classification; and it is evident, on glancing at the subject
cursorily, that any classification that brings together in groups
diseases that have considerable affinity, or that are liable to be
confounded with each other, is likely to facilitate the deduction
of general principles.
"Classification is a method of generalization. Several
classifications may therefore, be used with advantage; and the
physician, the pathologist, or the jurist, each from his own point
of view, may legitimately classify the diseases and the causes of
death in the way that he thinks best adapted to facilitate his
inquiries, and to yield general results.
"The medical practitioner may found his main divisions of
diseases on their treatment as medical or surgical; the
pathologist, on the nature of the morbid action or product; the
anatomist or the physiologist on the tissues and organs involved;
the medical jurist on the suddenness or the slowness of the death;
and all these points well deserve attention in a statistical
classification.
"In the eyes of national statists the most important elements
are, however, brought into account in the ancient subdivision of
diseases into plagues, or epidemics and endemics, into diseases of
common occurrence (sporadic diseases), which may be conveniently
divided into three classes, and into injuries, the immediate
results of violence or of external causes."
"Letter codes" are used to specify the type or category of ICD9 codes.
For example, the "Group" (72 Causes of Death grouping)
for measles, code G-011, contains the "Nature of Disease"
codes for measles, N-055,
including 055.0, 055.1, 055.2, 055.7, 055.8 and 055.9.
Generally, the best rule is specify the range(s) of ICD codes contained in a group code,
instead of specifying the group code value.
Thus, the query criteria should specify ICD9 055 - 055.9 for measles,
instead of ICD9 G011.
Datasets include limited ICD9 Codes, thus when you searching for
a specific code, it may not be included in a particular dataset.
For example, cancer incidence data do not include accident codes.
The following list describes the ICD9 Codes and associated datasets.
Publications of the World Health Organization enjoy copyright protection in accordance with the provisions
of Protocol 2 of the Universal Copyright Convention. For rights of reproduction or translation of WHO publications,
in part or in toto, application should be made to the Office of Publications, World Health Organization, Geneva,
Switzerland. The World Health Organization welcomes such applications.
Introduction to ICD10
A classification of diseases may be defined as a system of categories to which morbid entities are
assigned according to established criteria. There are many possible axes of classification and the one
selected will depend upon the use to be made of the statistics to be compiled. A statistical classification of
diseases must encompass the entire range of morbid conditions within a manageable number of categories.
The Tenth Revision of the International Statistical Classification of Diseases and Related Health Problems
is the latest in a series that was formalized in 1893 as the Bertillon Classification
or International List of Causes of Death . A complete review of the historical background
to the classification is given in Volume 2. While the title has been amended to make clearer the content
and purpose and to reflect the progressive extension of the scope of the classification beyond diseases
and injuries, the familiar abbreviation 'ICD' has been retained. In the updated classification,
conditions have been grouped in a way that was felt to be most suitable for general epidemiological purposes
and the evaluation of health care.
Work on the Tenth Revision of the ICD started in September 1983 when a Preparatory Meeting on
ICD-10 was convened in Geneva. The programme of work was guided by regular meetings of
Heads of WHO Collaborating Centres for Classification of Diseases. Policy guidance was provided by a
number of special meetings including those of the Expert Committee on the International Classification of
Disease - Tenth Revision, held in 1984 and 1987.
In addition to the technical contributions provided by many specialist groups and individual experts,
a large number of comments and suggestions were received from WHO Member States and Regional
Offices as a result of the global circulation of draft proposals for revision in 1984 and 1986. From the
comments received, it was clear that many users wished the ICD to encompass types of data other
than the 'diagnostic information' (in the broadest sense of the term) that it has always covered.
In order to accommodate the perceived needs of these users, the concept arose of a 'family' of
classifications centred on the traditional ICD with its familiar form and structure. The ICD itself would thus
meet the requirement for diagnostic information for general purposes, while a variety of other classifications
would be used in conjunction with it and would deal either with different approaches to the same
information or with different information (notably medical and surgical procedures and disablement).
Following suggestions at the time of development of the Ninth Revision of the classification that a
different basic structure might better serve the needs of the many and varied users, several alternative
models were evaluated. It became clear, however, that the traditional single-variable-axis design of the
classification, and other aspects of its structure that gave emphasis to conditions that were frequent, costly
or otherwise of public health importance, had withstood the test of time and that many users would be
unhappy with any of the models that had been proposed as a possible replacement.
Consequently, as study of the Tenth Revision will show, the traditional ICD structure has been retained
but an alphanumeric coding scheme replaces the previous numeric one. This provides a
larger coding frame and leaves room for future revision without disruption of the numbering system,
as has occurred at previous revisions.
In order to make optimum use of the available space, certain disorders of the immune
mechanism are included with diseases of the blood and blood-forming organs (Chapter III).
New chapters have been created for diseases of the eye and adnexa and diseases of the ear and
mastoid process. The former supplementary classifications of external causes and of factors influencing
health status and contact with health services now form part of the main classification.
The dagger and asterisk system of dual classification for certain diagnostic statements,
introduced in the Ninth Revision, has been retained and extended, with the asterisk axis being
contained in homogeneous categories at the three-character level.
The "dagger and asterisk" system in ICD10
ICD-9 introduced a system, continued in ICD-10, whereby there are two codes for diagnostic statements
containing information about both an underlying generalized disease and a manifestation in a
particular organ or site which is a clinical problem in its own right.
The primary code is for the underlying disease and is marked with a dagger (+);
an optional additional code for the manifestation is marked with an asterisk (*).
This convention was provided because coding to underlying disease alone was often unsatisfactory
for compiling statistics relating to particular specialties, where there was a desire to see the
condition classified to the relevant chapter for the manifestation when it was the reason for medical care.
While the dagger and asterisk system provides alternative classifications for the presentation of statistics,
it is a principle of the ICD that the dagger code is the primary code and must always be used.
Provision should be made for the asterisk code to be used in addition if the alternative method of presentation
may also be required. For coding, the asterisk code must never be used alone. Statistics incorporating the
dagger codes conform with the traditional classification for presenting data on mortality and morbidity and
other aspects of medical care.
Asterisk codes appear as three-character categories. There are separate categories for the same
conditions occurring when a particular disease is not specified as the underlying cause. For example,
categories G20 and G21 are for forms of Parkinsonism that are not manifestations of other diseases
assigned elsewhere, while category G22* is for "Parkinsonism in diseases classified elsewhere".
Corresponding dagger codes are given for conditions mentioned in asterisk categories; for example,
for Syphilitic parkinsonism in G22*, the dagger code is A52.1+.
Some dagger codes appear in special dagger categories. More often, however, the dagger code
for dual-element diagnoses and unmarked codes for single-element conditions may be derived from the
same category or subcategory.
The areas of the classification where the dagger and asterisk system operates are limited;
there are 83 special asterisk categories throughout theclassification, which are listed at the
start of the relevant chapters.
Rubrics in which dagger-marked terms appear may take one of three different forms:
(i)
If the symbol (+) and the alternative asterisk code both appear in the rubric heading,
all terms classifiable to that rubric are subject to dual classification and
all have the same alternative code, e.g.
| |
A17.0+
|
|
Tuberculous meningitis (G01*)
|
| | |
Tuberculosis of meninges (cerebral) (spinal)
|
| | |
Tuberculous leptomeningitis
|
(ii)
If the symbol appears in the rubric heading but the alternative asterisk code does not,
all terms classifiable to that rubric are subject to dual classification but
they have different alternative codes (which are listed for each term), e.g.
| |
A18.1+
|
|
Tuberculosis of genitourinary system
|
| | |
Tuberculosis of:
- bladder (N33.0*)
- cervix (N74.0*)
- kidney (N29.1*)
- male genital organs (N51.-*)
- ureter (N29.1*)
Tuberculous female pelvic inflammatory disease (N74.1*)
|
(iii)
If neither the symbol nor the alternative code appear in the title,
the rubric as a whole is not subject to dual classification but individual
inclusion terms may be; if so, these terms will be marked with the
symbol and their alternative codes given, e.g.
| |
A54.8
|
|
Other gonococcal infections
|
| | |
Gonococcal:
- peritonitis+ (K67.1*)
- pneumonia+ (J17.0*)
- septicaemia
- skin lesions
|
