Scientific Data Documentation
International Classification Of Diseases - 9 (1975)
ABSTRACT
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 nay 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."
BACKGROUND
Early History
Francois Bossier de Lacroix (1706-1777), better known as
Sauvages, first attempted to classify diseases systematically.
Sauvages' comprehensive treatise was published under the title
Nosologia Methodica. A contemporary of Sauvages was the great
methodologist Linnaeus (1707-1778), one of whose treatises was
entitled Genera Morborum. At the beginning of the 19th century,t
he classification of disease in most general use was one by William
Cullen (1710-1790), of Edinburgh, which was published in 1785 under
the title Synopsis Nosologiae Methodicae.
The statistical study of disease, however, began for all
practical purposes with the work of John Graunt on the London Bills
of Mortality a century earlier. In an attempt to estimate the
proportion of liveborn children who died before reaching the age of
six years, no records of age at death being available, he took all
deaths classed as thrush, convulsions, rickets, teeth and worms,
abortives, chrysomes, infants, livergrown, and overlaid and added
to them half the deaths classed as smallpox, swine pox, measles,
and worms without convulsions. Despite the crudity of this
classification his estimate of a 36 per cent mortality before the
age of six years appears from later evidence to have been a good
one. While three centuries have contributed something to the
scientific accuracy of disease classification, there are many who
doubt the usefulness of attempts to compile statistics of disease,
or even causes of death, because of the difficulties of
classification. To these, one can quote Major Greenwood (2): "The
Scientific purist, who will wait for medical statistics until they
are nosologically exact, is no wiser than Horace's rustic waiting
for the rive to flow away".
Fortunately for the progress of preventive medicine, the
General Register Office of England and Wales, at its inception in
1837, found in William Farr (1807-1883)-its first medical
statistician-a man who not only made the best possible use of the
imperfect classifications of disease available at the time, but
laboured to secure better classification and international
uniformity in their use.
Farr found the classification of Cullen in use in the public
services of his day. It had not been revised so as to embody the
advances of medical science, nor was it deemed by him to be
satisfactory for statistical purposes. In the first Annual Report
of the registrar General, therefore, he discussed the principles
that should govern a statistical classification of disease and
urged the adoption of a uniform classification.
Both nomenclature and statistical classification received
constant study and consideration by Farr in his annual "Letters" to
the Registrar General published in the Annual Reports of the
Registrar General. The utility of a uniform classification of
causes of death was so strongly recognized at the first
International Statistical Congress, held at Brussels, in 1853, that
it requested William Farr and Marc d'Espine, of Geneva, to prepare
"une nonmenclature uniforme des causes deces applicable a tous les
pays". (3) At the next Congress, at Paris in 1855, Farr and
d'Espine submitted two separate lists which were based on very
different principles. Farr's classification was arranged under
five groups: Epidemic diseases, Constitutional (general) diseases,
Local diseases arranged according to anatomical site, Developmental
diseases, and diseases that are the direct result of violence.
D'Espine classified diseases according to their nature (gouty,
herpetic, haematic, etc.). The Congress adopted a compromise list
of 138 rubrics. In 1864, this classification was revised at Paris
"sur le modele de celle de W. Farr", and was subsequently revised
in 1874, 1880, and 1886. Although there was never any universal
acceptance of this classification, the general arrangement,
including the principle of classifying diseases by anatomical site,
proposed by Farr has survived as the basis of the Internal List of
Causes of Death.
Adoption of International List of Causes of Death
The International Statistical Institute, the successor to the
International Statistical Congress, at its meeting in Vienna in
1891, charged a committee, of which Jacques Bertillon (1851-1922),
Chef des Travaux statistiques de la ville de Paris, was chairman,
with the preparation of a classification of causes of death. It is
of interest to note that Bertillon was the grandson of Achille
Guillard, a noted botanist and statistician, who had introduced the
resolution requesting Farr and d'Espine to prepare a uniform
classification at the First Statistical Congress in 1853. The
report of this committee was presented by Bertillon at the meeting
of the International Statistical Institute at Chicago in 1893 and
adopted by it. The classification prepared by Bertillon was based
on the classification of causes of death used by the City of Paris,
which, since its revision in 1885, represented a synthesis of
English, German, and Swiss classifications. The classification was
based on the principle, adopted by Farr, of distinguishing between
general diseases and those localized to a particular organ or
anatomical site. In accordance with the instructions of the Vienna
Congress made at the suggestion of L. Guillaume, the Director of
the Federal Bureau of Statistics of Switzerland, Bertillon included
three classifications: the first, an abridged classification of 44
titles; the second, a classification of 99 titles; and the third a
classification of 161 titles.
The Bertillon Classification of Causes of Death, as it was at
first called, received general approval and was adopted by several
countries, as well as by many cities. The classification was first
used in North America by Jesus E. Monjaras for the statistics of
San Luis de Potosi, Mexico. (4) In 1898, the American Public Health
Association, at its meeting in Ottawa, Canada, recommended the
adoption of the Bertillon Classification by registrars of Canada,
Mexico, and the United States. The Association further suggested
that the classification be revised every ten years.
The meeting of the International Statistical Institute at
Christiania in 1899, Bertillon presented a report on the progress
of the classification, including the recommendations of the
American Public Health Association for decennial revisions. The
International Statistical Institute then adopted the following
resolution:
"The International Statistical Institute, convinced of the
necessity of using in the different countries comparable
nomenclatures:
"Learns with pleasure of the adoption by all the statistical
offices of North America, by some of those of South America, and by
some in Europe, of the system of cause of death nomenclature
presented in 1893:
"Insists vigorously that this system of nomenclature be
adopted in principle and without revision, by all the statistical
institutions of Europe;
"Approves, at least in its general lines, the system of
decennial revision proposed by the American Public Health
Association at its Ottawa session (1898);
"Urges the statistical offices who have not yet adhered, to do
so without delay, and to contribute to the comparability of the
cause of the death nonmenclature." (5)
The French Government therefore convoked at Paris, in August
1900, the first International Conference for the revision of the
Bertillon or International Classification of Causes of Death.
Delegates from 26 countries attended this Conference. A detailed
classification of causes of death consisting of 179 groups and an
abridged classification of 35 groups were adopted on 21 August
1900. The desirability of decennial revisions was recognized, and
the French Government was requested to call the next meeting in
1910. Actually the next conference was held in 1909, and the
Government of France called succeeding conference inn 1920, 1929,
and 1938.
Bertillon continued as the guiding force in the promotion of
the International List of Causes of Death, and the revisions of
1900, 1910, and 1920 were carried out under his leadership. As
Secretary-General of the International Conference, he sent out the
provisional revision for 1920 to more than 500 persons, asking for
comments. His death in 1922 left the International Conference
without a guiding hand.
At the 1923 session of the International Statistical
Institute, Michel Huber, Bertillon's successor in France,
recognized this lack of leadership and introduced a resolution for
the International Statistical Institute to renew its stand of 1893
in regard to the International Classification of Causes of Death
and to co-operate with other international organizations in
preparation for subsequent revisions. The Health Organization of
the League of nations had also taken an active interest in vital
statistics and appointed a Commission of Statistical Experts to
study the classification of diseases and causes of death, as well
as other problems in the field of medical statistics. E. Roesle,
Chief of the Medical Statistical Service of the German Health
Bureau and a member of the Commission of Expert Statisticians,
prepared a monograph that listed the expansion in the rubrics of
the 1920 International List of Causes of Death that would be
required if the classification was to be used in the tabulation of
statistics or morbidity. This careful study was published by the
Health Organization of the League of Nations in 1928. (6) In order
to co-ordinate the work of both agencies, an international
commission, known as the "Mixed Commission", was created with an
equal number of representatives from the International Statistical
Institute and the Health Organization of the League of Nations.
This Commission drafted the proposals for the Fourth (1929) and the
Fifth (1938) revisions of the International List of Causes of
Death.
The Sixth, Seventh, and Eighth Revisions
The International Health Conference held in New York City in
1946 entrusted the Interim Commission of the World Health
Organization with the responsibility of undertaking preparatory
work for the next decennial revision of the International Lists of
Causes of Death and for the establishment of International Lists of
Causes of Morbidity (7). The International Conference for the
Sixth Revision of the International Lists of Diseases and Causes of
Death was convened in Paris in April 1949 by the Government of
France and its secretariat was entrusted jointly to the competent
French administrations and to the World Health Organization which
had carried out the preparatory work under the Arrangement
concluded by the governments represented at the International
Health Conference in 1946 (7).
The Sixth Decennial Revision Conference marked the beginning
of a new era in international vital and health statistics. Apart
from approving a comprehensive list for both mortality and
morbidity and agreeing on international rules for selecting the
underlying cause of death it recommended the adoption of a
comprehensive programme of international co-operation in the field
of vital and health statistics, including the establishment of
national committee on vital and health statistics for the purpose
of co-ordinating statistical activities in the country and to serve
as a link between the national statistical institutions and the
World Health Organization (8).
The International Conference for the Seventh Revision of the
International Classification of Diseases was held in Paris under
WHO auspices in February 1955 (9). In accordance with a
recommendation of the WHO Expert Committee on Health Statistics
(10) this revision was limited to essential changes and amendments
of errors and inconsistencies.
The Eighth Revision Conference convened by WHO met in the
Palais des Nations, Geneva, from 6 to 12 July 1965 (11). This
revision was of more radical nature than the Seventh but left
unchanged the basic structure of the Classification and the general
philosophy of classifying diseases according to their aetiology
rather than a particular manifestation.
REPORT OF THE INTERNATIONAL CONFERENCE FOR THE NINTH REVISION
General Information
The International Conference for the Ninth Revision of the
International Classification of Diseases convened by the World
Health Organization met at WHO headquarters in Geneva from 30
September to 6 October 1975. The Conference was attended by
delegations from 46 Member States:
Algeria Nigeria
Australia Norway
Austria Poland
Belgium Portugal
Brazil Saudi Arabia
Canada Singapore
Chad Spain
Denmark Sudan
Egypt Sweden
Finland Switzerland
France Thailand
German Democratic Republic Togo
Germany, Federal Republic of Trinidad and Tobago
Guatemala Tunisia
Hungary Union of Soviet Socialist Republics
India United Arab Emirates
Indonesia United Kingdom of Great Britain
Ireland and Northern Ireland
Israel United Republic of Cameroon
Italy United States of America
Japan Venezuela
Libyan Arab Republic Yugoslavia
Luxembourg Zaire
Netherlands, Kingdom of the
The United Nations, the Organization for Economic Cooperation
and Development, the International Labour Organization and the
International Agency for Research on Cancer sent representatives to
participate in the Conference, as did the Council for International
Organizations of Medical Sciences and ten other international non-
governmental organizations concerned with dental health,
dermatology, gynaecology and obstetrics, mental health,
dermatology, gynaecology and obstetrics, mental health,
neurosurgery, ophthalmology, paediatrics, pathology, radiology, and
rehabilitation of the disabled.
The Conference was opened by Dr. A. S. Pavlov, Assistant
Director-General, on behalf of the Director-General. Dr. Pavlov
reviewed the history of the ICD, reminding delegates that it had
developed from an International List of Causes of Death, first
agreed in 1893. WHO took over responsibility with the Sixth
Revision and its concern with the ICD is written into its
Constitution. Since WHO took over, there had been a great
extension of use of the ICD for the indexing and retrieval of
records and for statistics concerning the planning, monitoring and
evaluation of health services, besides its traditional use in
epidemiology.
The Conference elected the following officers:
Chairman: Dr. R. H. C. Wells (Australia)
Vice-Chairmen: Dr. J. M. Avilan-Rovira (Venezuela)
Dr. G. Cerkovnij (USSR)
Dr. I. M. Moriyama (United States of America)
Mr. G. Paine (United Kingdom)
Rapporteurs: Dr. M. S. Heasman (United Kingdom)
Dr. (Mlle) M. Guidevaux (France)
Secretariat: Dr. A. S. Pavlov (Assistant Director-General, WHO)
Mr. K. Uemura (Director, Division of Health
Statistics, WHO)
Dr. K. Kupka (Chief Medical Officer, International
Classification of Disease, WHO) (Secretary)
Mr. H. G. Corbett (Statistician, International
Classification of Diseases, WHO)
Professor G. G. Avtandilov (USSR) (Temporary
Adviser)
The Conference adopted an agenda dealing with the Ninth
Revision of the International Classification of Diseases, with
several provisional supplementary classifications intended for use
in conjunction with it, and with allied topics.
Ninth Revision of the International Classification of Diseases
Review of activities in the preparation of the proposals for
the Ninth Revision
The procedures leading up to the Ninth Revision commenced in
1969 with the calling of a Study Group. The work had been planned
and carried out so that the proposals before the Conference were in
a much more advanced state of preparation than had been the case at
earlier revisions. The intention was to have the completed manual,
with its alphabetical index, in the hands of users in good time to
allow for adequate training and familiarization in countries before
its introduction. The progress of preparations for revision had
been guided by further meetings of the Study Group and by meetings
of Heads of Centres for Classification of Diseases. The first
meeting of the Study Group considered that the revision ought to be
a limited one. It soon became clear, however, that a much more
radical revision was being demanded by specialists in many fields
of medicine. Views were sought from individual consultants,
international specialists bodies, the WHO Centres for
Classification of Diseases and headquarters units. Regional
offices arranged meetings so that representatives of Member States
could give their views. The third meeting of the Study Group
considered proposals incorporating views from all these sources,
and on the basis of their recommendations draft proposals were
circulated to Member States in mid-1973. Comments on the proposals
were considered by the WHO Expert Committee on Health Statistics in
June 1974 (12), and the proposals before the Conference were the
results of its recommendations. Delegates from several countries
spoke in support of the revision as proposed. In particular it was
reiterated that clinical pressures had demanded an extensive
revision at this stage on the grounds that he structure of several
of the ICD chapters was out of touch with modern clinical concepts.
The delegation from sweden, on behalf of the five Nordic countries
(Denmark, Finland, Iceland, Norway and Sweden), put forward the
view that the problems and cost associated with so extensive a
change would be substantial since these countries had established
a 5-digit version based on the ICD-8 which was widely used in
computerized health information systems. They considered that this
5-digit version met to a large extent the clinical demands for
greater specificity which the Ninth Revision was aiming at. The
Conference noted the concern of the Nordic countries but,
recognizing the need pointed out by several countries to satisfy
clinical requirements by structural changes as well as by providing
increased specificity, in general supported the scope of the
proposed revision as presented to the Conference.
History and Development of Uses of the ICD
The Conference was reminded of the impressive history of the
classification. Its origins lay in a list of causes of death,
which was used for many years. At the Sixth Revision, the
classification was extended to cover non-fatal conditions. Later
the classification had been shown to be useful for the purposes of
hospital indexing, particularly if adapted by means of some extra
subdivision. More recently adaptations had been made for use in
medical audit systems. The Ninth Revision proposals include a
device designed to improve its suitability for use in statistics
for the evaluation of medical care. For the future, it would have
to be decided what kind of adaptation of the ICD would render it
usable for Health Insurance Statistics, and whether it was possible
to adapt it as a basis for central payment for medical services.
All these uses tended to push the classification in the direction
of more detail. At the other end of the scale it had to be
remembered that there were demands from countries and areas where
such sophistication was irrelevant but which nevertheless would
like a classification based on the ICD so as to assess their
progress in health care and in the control of sickness.
General Characteristics of the Proposed Ninth Revision
The general arrangement of the proposals for the ninth
Revision considered by the Conference was much the same as in the
eighth Revision, though with much additional detail. care had
been taken to ensure that the categories were meaningful at the 3-
digit level. There were certain innovations:
(i) Optional fifth digits were provided in certain places: for
example for the mode of diagnosis in tuberculosis, for method of
delivery in chapter XI, for anatomical site in musculoskeletal
disorders and for place of accident in the E code.
(ii) An independent 4-digit coding system was provided to classify
histological varieties of neoplasm, prefixed by the letter M (for
morphology) and followed by a fifth digit indicating behavior.
This code was for optional use in addition to the normal code
indicating topography.
(iii) The role of the E code for external causes had changed. In
the Sixth, Seventh and Eighth Revisions, Chapter XVII consisted of
two alternative classifications, one according to the nature of the
injury (the N code) and one according to external cause (the E
code). In the Ninth Revision it was proposed to drop the N prefix
and consider only the nature of injury as part of the main
classification. The E code becomes a supplementary classification
to be used, where relevant in conjunction with codes form any part
of the classification. For mortality statistics, however, the E
code should still be used in preference to Chapter XVII in
presenting underlying causes of death, when only one is used.
(iv) The Ninth Revision proposals included dual classification of
certain diagnostic statements. The Conference heard that the
system had been introduced into the 1973 proposals after it had
become obvious that there was a demand to classify diseases
according to important manifestations, e.g. to classify numps
encephalitis to a category for encephalitis. It would have been
unwise to change the whole axis of the ICD to this basis, so the
first proposal was to make the positioning according to
manifestation alternative to the traditional placing according to
aetiology. As a result of criticism, it is now proposed that the
"traditional" aetiology codes, those marked with a+, should be
considered primary, and the new codes, positioned in the
classification according to manifestation and marked with an *,
should be secondary, for use in applications concerned with the
planning and evaluation of medical care. This system applies only
to diagnostic statements that contain information about both
etiology and manifestation and when the latter is important in its
own right.
(v) Categories in the Mental Disorders Chapter include
descriptions of their content with a view to overcoming the
particular difficulties in this field, where international
terminology is not standard.
The V code (formerly the Y code) continues to appear in Volume 1.
These characteristics of the proposed revision were accepted by the
Conference.
Adoption of the Ninth Revision of the InternationalClassification of
Diseases.
The Conference,
Having considered the proposals prepared by the Organization
on the recommendations of the Expert Committee on Health Statistics
(12),
Recognizing the need for a few further minor modifications to
meet the comments on points of detail submitted by Member States
during the Conference,
Recommends that the revised Detailed List of Categories and
Sub-Categories in Annex I. to this report constitute the Ninth
Revision of the International Classification of Diseases.
Classification of Procedures in Medicine
In response to requests from a number of Member States, the
Organization had drafted a classification of therapeutic,
diagnostic and prophylactic procedures in medicine, covering
surgery, radiology, laboratory and other procedures. Various
national classifications of this kind had been studied and advice
sough from hospital associations in a number of countries. The
intention was to provide a tool for use in the analysis of health
services provided to patients in hospitals, clinics, outpatient
departments, etc.
The Conference congratulates the Secretariat on this important
development and
Recommends that the provisional procedures classifications
should be published as supplements to, and not as integral parts of
the Ninth Revision of the International Classification of Diseases.
They should be published in some inexpensive form and, after two or
three years' experience, revised in the light of users' comments.
Classification of Impairments and Handicaps
The ICD provided the means of classifying current illness or
injury; the classification of procedures provided a means of coding
the treatment or other services consumed by the patient. There
remained a need to classify impairments and the consequent
handicaps or disadvantages.
This was an area in which much development was occurring and
a draft classification had been prepared by the Organization
although this was to a large extent experimental and exploratory.
It had been drafted after much consultation with agencies
responsible for social services and rehabilitation.
The Conference having considered the classification of
Impairments and Handicaps believes that these have potential value
and accordingly
Recommends that the Impairments and Handicaps classifications
be published for trial purposes as a supplement to, and not as an
integral part of, the Ninth Revision of the International
Classification of Diseases.
Adaptations of ICD for the Use of Specialists
The Conference noted three adaptations of the ICD which had
been designed for the sue of specialists.
The first was an adaptation for oncology-ICD-O. Coding was on
three axes indicating the topography, morphology and behaviour of
tumours. The 4-digit topography code was based on the list of sites
of the malignant neoplasm section of Chapter II of the Ninth
Revision of the ICD, but was to be used for any type of neoplasm.
To this would be added a 4-digit code indicating histological
variety of neoplasm, and a single-digit code indicating behaviour.
It was intended that the code should be used by centres requiring
to record extra detail about tumours, as an alternative to the
Ninth Revision of ICD, with which it was entirely compatible. (A
conversion guide would be available, enabling translation of codes
by computer if desired.)
Other adaptations had been produced for dentistry and
stomatology and for ophthalmology. Each of these contains, a small
volume, all conditions of interest to the specialist, selected from
all chapters of the ICD, and provides additional detail by means of
a fifth digit.
Lay Reporting
The Conference discussed the problem of securing badly needed
morbidity and mortality statistics in countries still suffering
from a lack of sufficiently qualified personnel. There was a
divergence of opinion concerning the system of classification to be
used where information about sickness or causes of death is
necessarily furnished by persons other than physicians. Some
delegates considered that the International Classification of
Diseases in some simplified form (e.g. one of the tabulation lists)
would serve this purpose while others believed that a system
independent of the ICD needed to be established.
A small working party, consisting of delegates from Member
States with experience of the problem, was convened to consider the
question in more detail and in the light of its report
The Conference,
Realizing the present problem involved in the full utilization
of ICD by the developing countries in most of the regions;
Recognizing the need for introducing a system which could
provide useful and objective morbidity and mortality data for
efficient health planning;
Appreciating the field trials conducted in some countries for
collection of morbidity and mortality information through non-
medical health or other personnel and the experience thus obtained;
Noting the concern of the World Health Organization for
development and promotion of health services, particularly in the
developing countries, as contained in resolutions EB55.R16 (13),
WHA28.78 (14), WHA28.77 (15) and WHA28.88 (16),
Recommends that the World Health Organization should
(1) become increasingly involved in the attempts made by the
various developing countries for collection of morbidity and
mortality statistics through lay or paramedical personnel;
(2) organize meetings at regional level for facilitating exchange
of experiences between the countries currently facing this problem
so as to design suitable classification lists with due
consideration to national differences in terminology;
(3) assist countries in their endeavor to establish or expand the
system of collection or morbidity and mortality data through lay or
paramedical personnel.
Statistics of Death in the Perinatal Period and Related Matters
The conference considered with interest the reports of the
Scientific Group on Health Statistics Methodology relating to
Perinatal Events (17) and the recommendations of the Expert
Committee (12) on this subject. These were the culmination of a
series of special WHO meetings attended by specialists from many
disciplines. It had become clear that a review of the situation
was needed in the light of certain developments in medical
sciences, notably those leading to the improved survival of infants
born at a very early gestational age.
After discussion, the Conference
Recommends that, where practicable, statistics in relation to
perinatal deaths should be derived from a special certificate of
perinatal death (instead of the normal death certificate) and
presented in the manner set out in Annex II, which also includes
relevant definitions. This annex also includes recommendations in
respect of maternal mortality statistics.
Mortality Coding Rules
The Conference was made aware of the problems arising in
selecting the underlying cause of death where this was the result
of factors connected with surgical or other treatment. It was
proposed that where ann untoward effect of treatment is responsible
for death then this should be coded rather than the condition for
which the treatment was given. Although there were views expressed
by some delegates that this interfered with the traditional
underlying cause concept, the Conference preferred the former view
and accordingly
Recommends that the modification rule in Annex III be added to
the existing rules for selection of cause of death for primary
mortality tabulation.
The Conference was also informed that additional guidelines
for dealing with certificates of death from cancer had been drafted
and were being tested in several countries. If the tests showed
that the guidelines improved consistency in coding, they would be
incorporated into the Ninth Revision.
Selection of a Single Cause for Statistics or Morbidity
No rules had hitherto been incorporated into the ICD
concerning the tabulation of morbidity. Routine statistics are
normally based upon a single cause and the Conference considered
that the application of the ICD to routine morbidity statistics had
reached a point where international recommendations for selection
of single cause for presentation of morbidity statistics was
appropriate and accordingly
Recommends that the condition to be selected for single-cause
analysis for health-care records should be the main condition
treated or investigated during the relevant episode of hospital or
other care. If no diagnosis was made, the main symptom or problem
should be selected instead. Whenever possible, the choice should
be exercised by the responsible medical practitioner or other
health-care professional and the main condition or problem
distinguished from other conditions or problems.
Short Lists for Tabulation of Mortality and Morbidity
Difficulties had become apparent in the use of the present
short lists A, B, C and D for the tabulation of mortality and
morbidity. Their construction and numbering was such that
confusion often arose and comparability of statistics based on
different lists presented some difficulties. Proposed new lists
were presented to the Conference in which totals were shown for
groups of diseases and for certain selected individual conditions.
Minimum lists of 55 items were recommended for the tabulation of
mortality and morbidity and countries could add to these further
items from a basic list of 275 categories.
The Conference
Recommends that the Special Tabulation Lists set out in Annex
IV to this report should replace the lists for tabulation of
morbidity and mortality and should be published as part of the
International Classification of Diseases together with appropriate
explanation and instruction as to their use.
Multiple Condition Coding and Analysis
The Conference noted with interest the extended use of
multiple condition coding and analysis in a number of countries
with a variety of ends in view. One example was the study of the
interrelationship of various conditions recorded on a death
certificate; another was to permit computer selection of the
underlying cause of death. The Conference also noted the value of
a store of multiple-coded national data on mortality and morbidity.
The Conference expressed encouragement of such work but did not
recommend that the ICD should contain any particular rules or
methods of analysis to be followed.
Different Disease-Coding Systems
The Conference was reminded of the existence of other disease
classifications and reviewed their attributes as a preliminary to
discussion of the possible form of the Tenth Revision. Some of
these classifications are developments from the International
Classification of Diseases; other are multi-axial, enabling
retrieval from different viewpoints but not primarily designed with
the presentation of routine statistics in mind. In others, a
unique code is given to each disease or term, enabling retrieval of
specific conditions and assembly into alternative classifications
according to need. These developments seemed to indicate some
desire for greater flexibility and to raise doubts as to whether a
single multi-purpose classification was any longer practicable. It
was felt that multi-axial classification often destroyed the
ability to retrieve disease terms. Allocating a unique code to a
disease or term might be one way of over-coming problems caused by
changes in classification.
Tenth Revision of the International Classification of Diseases
The Conference recognized the need to make an early start in
planning the next revision of the classification and discussed a
number of questions that needed to be settled before detailed work
could begin. The most fundamental point was that the
Organization's programme was no longer confined to disease
classification alone. Many other reasons, social and economic, for
contact with health services were now included in the main
classification and supplementary classifications of procedures in
medicine and impairments and handicaps had been added. These
needed to be further developed and incorporated into a
comprehensive and coordinated system of classifications of health
information. The name of the Organization's programme should
reflect the wider scope of its activities.
Standardization of nomenclature on a multilingual basis was
essential for conformity in diagnosis, and glossaries similar to
the one developed for psychiatry might be provided for other
specialties where diagnostic concepts were unclear. A lack of
balance in the Eight Revision, which contained 140 categories for
infectious diseases but only 20 for the whole of perinatal
morbidity, had been retained in the Ninth Revision because of its
essentially conservative nature, but such a restriction should not
necessarily hold for the next revision.
It was acknowledged that conflicts existed between the need
for a fairly broad classification for the purpose of international
comparisons and the desire for a very high degree of specificity
for diagnostic indexing and for epidemiological research, and
between the requirements of a classification usable at the
community level in developing countries and one suitable for a
national morbidity programme with access to a computer. The
structure of the Tenth Revision was another question for urgent
decision; should the present uni-axial system be retained or should
there be a move to a multi-dimensional approach; should the coding
and classification elements be separated so that the former could
remain constant while the latter could be revised at shorter
intervals than at present?
The view of the Conference was that these questions should be
decided within the next two or three years by the construction and
trial of model classifications of various types. It was recognized
that this would be an additional task to the normal work of the
Organization in this area and would require the provision of extra
resources.
The Conference recognized the great value of the work already
done and still being done on ICD; it also recognized the rapidly
increasing demands for more flexibility than is available in the
present structure of this classification.
The Conference,
Noting that the ICD, despite the present constraints upon
resources, which it completely absorbs, is one of the most
influential activities of WHO,
Recommends that:
(1) WHO should continue its work in developing revisions of the
ICD and related classifications and that the Organization's
activity in connexion with the revision of the ICD should be
expanded;
(2) the ICD programme should be given sufficient resources to
enable it simultaneously to explore the needs for new departures in
the realm of health classifications and how these can be met
without detracting from the present revision process; the programme
should also be enabled to carry out extensive field trials of the
various alternative approaches that exist or which may emerge.
The Conference expressed the hope that efforts would be made
to retain the continuity of expertise that had been developed in
the Organization, in the centres for classification of diseases and
among numerous organizations and individuals throughout the world.
Publication of the Ninth Revision
The Conference was informed that although the Tabular List of
the ICD (Volume 1) in English and French could be made available in
published form by the end of 1976, it was unlikely that the
alphabetical Index (Volume 2) could be published before the middle
of 1977. The Russian and Spanish versions should follow the
English and French fairly closely.
Member States intending to publish national language versions
would receive pre-publication copies of the various parts of the
classification as and when they were completed by the Secretariat
to enable them to adhere as nearly as possible to this timetable.
Several delegates pointed out that the late appearance off the
alphabetical indexes at the Eight Revision had resulted in a high
rate of coding errors during the first year of use.
Because of the large amount of work still to be done before
the Ninth Revision can be published and because the training of
coders requires that both volumes, including the alphabetical
index, should be inn the hands of users some 12 months before it is
due to come into use,
The Conference
Recommends that the Ninth Revision of the International
Classification of Diseases should come into effect on 1 January
1979.
Familiarization and Training in the Use of the Ninth Revision
There were many aspects of the proposed revision, besides the
change in the categories themselves, which would require very
careful explanation to coders and to users of statistics based on
the ICD. It was planned that familiarization courses would be
organized by the WHO regional offices, to help Member countries in
planning their own courses. The Conference noted with interest
that WHO hoped to prepare a set of training material covering an
instructional course for coders of approximately two weeks, to make
sure that the instruction was as consistent as possible. WHO would
also make available explanatory material for users of statistics.
ADOPTION OF THE NINTH REVISION
The Twenty-ninth World Health Assembly, meeting in Geneva in
May 1976, adopted the following resolution with regard to the
Manual of the International Classification of Diseases (Resolution
WHA29.34) (18).
The Twenty-ninth World Health Assembly,
Having considered the report of the International Conference
for the Ninth Revision of the International Classification of
Diseases,
1. Adopts the detailed list of three-digit categories and optional
four digit sub-categories recommended by the Conference as the
Ninth Revision of the International Classification of Disease, to
come into effects as from 1 January 1979;
2. Adopts the rules recommended by the Conference for the
selection of a single cause in morbidity statistics;
3. Adopts the recommendations of the Conference regarding
statistics of perinatal and maternal mortality, including a special
certificate of cause of perinatal death for use where practicable;
4. Requests the Director-General to issue a new edition of the
Manual of the International Classification of Disease (Resolution
WHA29.35) (19).
The Twenty-ninth World Health Assembly.
Noting the recommendations of the International Conference for
the Ninth Revision of the International Classification of Diseases
in respect of activities related to the Classification,
1. Approves the publication, for trial purposes, of supplementary
classifications of Impairments and Handicaps and of Procedures in
Medicine as supplements to, but not as integral parts of, the
International Classification of Diseases;
2. Endorses the recommendation of the Conference concerning
assistance to developing countries in their endeavor to establish
or expand the system of collection of morbidity and mortality
statistics through lay or paramedical personnel;
3. Endorses the request made by the Executive Board in resolution
EB57.R34 (20) to the Director-General that he investigate the
possibility of preparing an International Nonmenclature of Diseases
as an improvement to the Tenth Revision of the International
Classification of Diseases.
MANUAL OF THE NINTH REVISION
Conventions Used in the Tabular List
The Tabular List makes special use of parentheses and colons
which needs to be clearly understood. When parentheses are used
for their normal function of enclosing synonyms, alternative
wordings or explanatory phrases, square brackets +...+ are
employed. Round brackets (...) are used to enclose supplementary
words which may be either present or absent in the statement of a
diagnosis without affecting the code number to which it is
assigned. Words followed by a colon +:+ are not complete terms, but
must have one or other of the understated modifiers to make them
assignable to the given category. "NOS" is an abbreviation for
"not otherwise specified" and is virtually the equivalent of
"unspecified" and "unqualified".
As an example of the use of the above conventions, category
464.0, Acute laryngitis, includes the following terms:
Laryngitis (acute):
NOS
Haemophilus influenzae +H. influenzae+
oedematous
pneumococcal
septic
suppurative
ulcerative
This signifies that to this category should be assigned
laryngitis, with or without the adjective "acute", if standing
alone or if accompanied by one or other of the modifiers:
Haemophilus influenzae +of which H. influenzae is an alternative
wording+, oedematous, pneumococcal, septic, suppurative, or
ulcerative. Influenzal, streptococcal, diphtheritic, tuberculous,
and chronic laryngitis will be found in other categories.
Dual Classification of Certain Diagnostic Statements
The Ninth Revision of the ICD contains an innovation that
there are two codes for certain diagnostic descriptions which
contain elements of information both about a localised
manifestation or complications and about a more generalised
underlying disease process. One of the codes-marked with a dagger
(+) - is positioned in the part of the classification in which the
diagnostic description is located according to normal ICD
principles, that relating to the underlying disease, and the other
- marked with an asterisk (*) - is positioned in the chapter of the
classification relating to the organ system to which the
manifestation of complication relates. Thus tuberculous meningitis
has its dagger code in the chapter for infectious and parasitic
diseases, and its asterisk code in the nervous system chapter.
The necessity for this arose from the desire of specialists
and those concerned with statistics of medical care to have certain
manifestations which are medical-care problems in their own right
classified in the chapters relating to the relevant organ system.
The ICD has traditionally classified generalised diseases and
infectious disease entities which may affect several parts of the
body to special chapters of the classification, and their
manifestations are normally assigned to the same place, so that
until now tuberculous meningitis has been classifiable only to the
infectious and parasitic diseases chapter.
The dagger and asterisk categories are in fact alternative
positionings in the classification for the relevant conditions,
enabling retrieval or statistical analysis from either viewpoint.
It is, however, a principle of ICD classification that the dagger
category is the primary code and that the asterisk code is
secondary, so it is important where it is desired to work with the
asterisk code, and both are used, to use some special mark or a
predetermined positioning in the coded record, to identify which is
the dagger, and which the asterisk, code for the same entity.
The criteria adopted in the Ninth Revision are that asterisk
categories are provided:
(i) if the manifestation or complication represents a medical-care
problem in its own right and is normally treated by a specialty
different from the one which would handle the underlying condition,
and
(ii) if the information about both the manifestation and the
underlying condition is customarily contained in one diagnostic
phrase (such as "diabetic retinitis"), or
(iii) if the category relating to the manifestation is subdivided
according to the cause-an example is arthropathy in which the
subdivisions relate to broad groups of causes.
Other underlying condition/manifestation combinations exist
which do not cause coding and retrieval problems and have therefore
not been incorporated in the "dagger and asterisk" system.
Examples are:
(i) situations where the two elements are customarily recorded as
discrete diagnostic phrases and can be dealt with simply by coding
the two terms separately, e.g. certain types of anaemia which may
be the consequence of other diseases; the classification of the
anaemia is usually according to its morphological type and does not
depend on the cause;
(ii) where the manifestation is an intrinsic part of the basic
disease and is not regarded as a separate medical-care problem; for
example, cholera, dysentery, etc. in the infectious and parasitic
diseases chapter do not have asterisk categories in the digestive
system chapter; lower genito-urinary tract manifestations of
venereal diseases, in the infectious and parasitic diseases
chapter, do not have asterisk categories in the genito-urinary
diseases chapter, although gonococcal salpingitis and orchitis do;
(iii) where the ICD has traditionally classified the condition
according to the manifestation, e.g. anaemia due to enzyme defect.
The areas of the Classification where the dagger and asterisk
system operates are limited; there are about 150 rubrics of each in
which asterisk-or dagger-marked terms occur. They may take one of
three different forms:-
(i) if the symbol (+ or *) and the alternative code both appear in
the title of the rubric, all terms classifiable to that rubric are
subject to dual classification and all have the same alternative
code, e.g.
049.0+ Lymphocytic choriomeningitis (321.6*)
Lymphocytic:
meningitis (serous)
meningoencephalitis (serous)
321.2* Meningitis due to ECHO virus (047.1+)
Meningo-eruptive syndrome
(ii) if the symbol appears in the title but the alternative 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.
074.2+ Coxsackie carditis
Aseptic myocarditis of Coxsackie:
newborn (422.0*) endocarditis (421.1*)
myocarditis (422.0*)
pericarditis (420.0*)
420.0* Pericarditis in diseases classified elsewhere
Pericarditis (acute): Pericarditis (acute):
Coxsackie (074.2+) tuberculous (017.8+)
meningococcal (036.4+) uraemic (585+)
syphilitic (093.8+)
(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, there terms will be
marked with the symbol and their alternative codes, e.g.
078.5 Cytomegalic inclusion disease
Cytomegalic inclusion virus hepatitis+ (573.1*)
Salivary gland virus disease
424.3 Pulmonary valve disorders
Pulmonic regurgitation:
NOS
syphilitic* (093.2+)
The use of asterisk coding is entirely optional. It should
never be employed in coding the underlying cause of death (only
dagger coding should be used for this purpose) but may be used in
morbidity coding and in multiple-condition coding whether in
morbidity or mortality. Any published tabulations, whether
according to the detailed list or one of the short lists, of
frequencies based on asterisk coding should be clearly annotated
"Based on ICD asterisk coding".
Role of the E Code
As explained in the Report of the International Revision
Conference (see paragraph 1.3 (iii), page XVI), the E Code is now
a supplementary classification that may be used, if desired, to
code external factors associated with morbid conditions classified
to any part of the main classification. For single-cause
tabulation of the underlying cause of death, however, the E Code
should be used as the primary code if, and only if, the morbid
condition is classifiable to Chapter XVII (Injury and Poisoning).
Gaps in the Numbering System
It will be noticed that certain code number have not been
used, leaving gaps in the numbering system. The reason for this
practice was to avoid unnecessary change sin code numbers familiar
to coders who have been using the Eighth Revision) has been moved
to category 785.4; in order to avoid changing the code numbers of
categories 446 (Polyarteritis nodosa and allied conditions), 447
(Other disorders of arteries and arterioles) and 448 (Diseases of
capillaries), it was preferred to leave the code number 445 unused
in the Ninth Revision.
Glossary of Mental Disorders
A glossary describing and defining the content of rubrics in
Chapter V (Mental Disorders) was published separately from the
Eighth Revision of the International Classification of Diseases.
in the Ninth Revision, the glossary has been incorporated into the
Classification itself (see pages 177-213).
The glossary descriptions are not intended as an aid for the
lay coder, who should code whatever diagnostic statement appears on
a medical record according to the provisions of the Tabular List
and Alphabetical Index. Their purpose is to assist the person
making the diagnosis, who should do so on the basis of the
descriptions rather than the category titles, which may differ in
meaning from place to place.
ADAPTATIONS OF THE ICD
Dentistry and Stomatology
The "Application of the ICD to Dentistry and Stomatology"
(ICD-DA), based on the Eighth Revision of the ICD, was prepared by
the Oral Health Unit of WHO and firs published in 1969. It brings
together those ICD categories that include "diseases or conditions
that occur in, have manifestations in, or have associations with
the oral cavity and adjacent structures". It provides greater
detail by means of a fifth digit, but the numbering system is so
organized that the relationship between an ICD-DA code and the ICD
code from which it is derived is immediately obvious and
frequencies for ICD-DA categories can be readily aggregated into
ICD categories.
ICD-DA has been revised to concord with the Ninth Revision of
the ICD and this revision was published by the World Health
Organization in 1977.
Oncology
The "International Classification of Diseases for Oncology"
(ICD-O) was published by the World Health Organization in 1976.
Developed in collaboration with the International Agency for
Research on Cancer (WHO) and the United States National Cancer
Institute, with input from many other counties and extensive field
trials, the ICD-O is intended for use in cancer registries,
pathology departments and other agencies specializing in cancer.
ICD-O is a dual-axis classification, providing coding systems
for topography and morphology. The topography code uses for all
neoplasms the same three- and four-digit categories that the Ninth
Revision of ICD uses for malignant neoplasms (categories 140-199),
thus providing increased specificity of site for other neoplasms,
where the ICD provides a more restricted topographical
classification or none at all.
The morphology code is identical to the neoplasms section of
the morphology field of the Systematized Nomenclature of Medicine
(SNOMed) (21) and is compatible with the 1968 Edition of the Manual
of Tumor Nomenclature and Coding (MOTNAC) (22) and the Systematized
Nomenclature of Pathology (SNOP) (23). It is a five-digit code,
the first four digits identifying the histological type and the
fifth the behaviour of the neoplasm (malignant, in situ, benign,
etc.). The ICD-O morphology code also appears in this Volume (see
pages 667-690) and in the Alphabetical Index.
In addition to the topography and morphology codes, ICD-O also
includes a list of tumour-like lesions and conditions. A table
explaining the method of converting ICD-O codes into ICD codes will
be published in due course.
Ophthalmology
The International Council of Ophthalmology, supported by
ophthalmological groups in many countries, has prepared a
Classification of Disorders of the Eye, based on the Ninth Revision
of the ICD.
In addition to the ICD section "Disorders of the eye and
adnexa" (categories 360-379), it includes all other ICD categories
that classify eye disorders, from infectious diseases to injuries.
It is a five-digit level but introducing additional detail at the
fifth digit for the use of specialists.
The classification was published in the "International
Nomenclature of Ophthalmology" by the American Academy of
Ophthalmology and Otolaryngology (24) in 1977, which also includes
definitions or short descriptions of all terms, synonyms and
equivalent terms in French, German and Spanish, and reference terms
to facilitate literature retrieval.
WHO CENTERS FOR CLASSIFICATION OF DISEASES
Six WHO Centres have been established to assist countries with
problems encountered in the classification of diseases and, in
particular, in the use of the ICD. They are located in
institutions in Paris (for French language users), Sao Paulo (for
Portuguese), Moscow (for Russian) and Caracas (for Spanish); there
are two Centres for English language users, in London and, for
North America, in Washington, D.C., USA. Communications should be
addressed as follows:-
Head, WHO Centre for Classification of Diseases
Office of Population Censuses and Surveys
St. Catherine's House
10 Kingsway
London WC2B 6JP
United Kingdom
or
Head, WHO Center for Classification of Diseases for North America
National Center for Health Statistics
US Public Health Service
Department of Health, Education and Welfare
Washington, DC.,
United States of America
REFERENCES
1. Registrar General of England and Wales, Sixteenth Annual
Report, 1856, Appendix, 75-76
2. Greenwood, M. (1948) Medical statistics from Graunt to Farr.
Cambridge, p. 28
3. Registrar General of England and Wales, Sixteenth Annual
Report, 1856, Appendix, p. 73
4. Bertillon, J. (1912) Classification of the causes of death.
(Abstract). Trans. 15th Int. Cong. Hyg. Demog.,
Washington, pp. 52-55
5. Bull. Inst. int. Statist. 1900, 12, 280
6. ROESLE, E. (1928) Essai d'une statistique comparative de la
morbidite devant servir a etablir les listes speciales des
causes de morbidite. Geneva (League of nations Health
Organization, document C.H. 730)
7. Off. Rec. Wld Hlth Org., 1948, 2, 110
8. Off. Rec. Wld Hlth Org., 1948, 11, 23
9. World Health Organization (1955) Report of the International
Conference for the Seventh Revision of the International
Classification of Diseases, Geneva (unpublished document
WHO/HS/8 Rev. Conf./17 Rev.1)
10. Wld Hlth Org. techn. Rep. Ser., 1952, 53
11. World Health Organization (1965) Report of the International
Conference for the Eighth Revision of the International
Classification of Diseases, Geneva (unpublished document
WHO/HS/8 Rev. Conf./17 Rev.1 )
12. World Health Organization, Expert Committee on Health
Statistics (1974) Ninth Revision of the International
Classification of Diseases, Geneva (unpublished document
WHO/ICD9/74.4)
13. Off. Rec. Wld Hlth Org., 1975, 223, 10
14. Off. Rec. Wld Hlth Org., 1975, 227, 42
15. Off. Rec. Wld Hlth Org., 1975, 226, 44
16. Off. Rec. Wld Hlth Org., 1975, 226, 53
17. World Health Organization, Scientific Group on Health
Statistics Methodology related to Perinatal Events (1974),
Geneva (unpublished document ICD/PE/74.4)
18. Off. Rec. Wld Hlth Org., 1976, 233, 18
19. Off. Rec. Wld Hlth Org., 1976, 233, 18
20. Off. Rec. Wld Hlth Org., 1976, 231, 25
21. College of American Pathologists (1976), Systematized
Nomenclature of Medicine, Chicago, Illinois
22. American Cancer Society, Inc. (1968), Manual of Tumor
Nomenclature of Medicine, Chicago, Illinois
23. College of American Pathologists (1965), Systematized
Nomenclature of Pathology, Chicago, Illinois
24. American Academy of Ophthalmology and Otolaryngology (1977),
International Nomenclature of Ophthalmology, 15 Second Street,
S.W., Rochester, Minnesota 55901.
