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.

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