Chapter 8 CLASSIFICATION OF DATA The principal value of vital statistics data is realized through the presentation of rates, which are computed by relating the vital events of a class to the population of a similarly defined class. Vital statistics and population statistics must therefore be classified according to similarly defined systems and tabulated in comparable groups. Even when the variables common to both, such as geographic area, age, sex, and race, have been similarly classified and tabulated, differences between the enumeration method of obtaining population data and the registration method of obtaining vital statistics data may result in significant discrepancies. The general rules used in the classification of geographic and personal items for deaths and fetal deaths for 1988 are set forth in two NCHS instruction manuals (1,2). A discussion of the classification of certain important items is presented below. Classification by occurrence and residence Tabulations for the United States and specified geographic areas in this volume are by place of residence unless stated as by place of occurrence. Before 1970, resident mortality statistics for the United States included all deaths occurring in the United States, with deaths of "nonresidents of the United States" assigned to place of death. "Deaths of nonresidents of the United States" refers to deaths that occur in the United States of nonresident aliens, nationals residing abroad, and residents of Puerto Rico, the Virgin Islands, Guam, and other territories of the United States. Beginning with 1970, deaths of nonresidents of the United States are not included in tables by place of residence. Tables by place of occurrence, on the other hand, include deaths of both residents and nonresidents of the United States. Consequently, for each year beginning with 1970, the total number of deaths in the United States by place of occurrence was somewhat greater than the total by place of residence. For 1988 this difference amounted to 3,197 deaths. Mortality statistics by place of occurrence are shown in tables 1-11, 1-19, 1-20, 1-29, 1-30, 3-1, 3-8, 8-1, and 8-7. Before 1970, except for 1964 and 1965, deaths of nonresidents of the United States occurring in the United States were treated as deaths of residents of the exact place of occurrence, which in most instances was an urban area. In 1964 and 1965, deaths of nonresidents of the United States occurring in the United States were allocated as deaths of residents of the balance of the county in which they occurred. Residence error--Results of a 1960 study showed that the classification of residence information on the death certificates corresponded closely to the residence classification of the census records for the decedents whose records were matched (3). A comparison of the results of this study of deaths with those for a previous matched record study of births (4) showed that the quality of residence data had considerably improved between 1950 and 1960. Both studies found that events in urban areas were overstated by the NCHS classification in comparison with the U.S. Bureau of the Census classification. The magnitude of the difference was substantially less for deaths in 1960 than it was for births in 1950. clsmor88.doc - Page 1 The improvement is attributed to an item added in 1956 to the U.S. Standard Certificates of Birth and of Death, asking if residence was inside or outside city limits. This new item aided in properly allocating the residence of persons living near cities but outside the corporate limits. Geographic classification The rules followed in the classification of geographic areas for deaths and fetal deaths are contained in the two instruction manuals referred to previously (1,2), The geographic codes assigned by the National Center for Health Statistics during data reduction of source information on birth, death, and fetal-death records are given in another instruction manual (5). Beginning with 1982 data, the geographic codes were modified to reflect results of the 1980 census. For 1970-81, codes are based on results of the 1970 census. Standard metropolitan statistical areas--The standard metropolitan statistical areas (SMSA's) used in this volume are those established by the U.S. Office of Management and Budget (6) from final 1980 census population counts and used by the U.S. Bureau of the Census, except in the New England States. Except in the New England States, an SMSA is a county or a group of contiguous counties containing a city of 50,000 inhabitants or more or an urbanized area of 50,000 with a total metropolitan population of at least 100,000. In addition to the county or counties containing such a city or urbanized area, contiguous counties are included in an SMSA if, according to specified criteria, they are essentially metropolitan in character and are socially and economically integrated with the central city or urbanized area (7). In the New England States the U.S. Office of Management and Budget uses towns and cities rather than counties as geographic components of SMSA's. The National Center for Health Statistics cannot, however, use the SMSA classification for these States because its data are not coded to identify all towns. Instead, NCHS uses New England County Metropolitan Areas (NECMA's). Made up of county units, these areas are established by the U.S. Office of Management and Budget (7,8). Metropolitan and nonmetropolitan counties--Independent cities and counties included in SMSA's or in NECMA's are included in data for metropolitan counties; all other counties are classified as nonmetropolitan. Population-size groups--Vital statistics data for cities and certain other urban places in 1988 are classified according to the population enumerated in the 1980 Census of Population. Data are available for individual cities and other urban places of 10,000 or more population. Data for the remaining areas not separately identified are shown in the tables under the heading "balance of area" or "balance of county." For the years 1970-81, classification of areas was determined by the population enumerated in the 1970 Census of Population. Beginning with 1982 data, as a result of changes in the enumerated population between 1970 and 1980, some urban places identified in previous reports are no longer included, and a number of other urban places have been added. Urban places other than incorporated cities for which vital statistics data are shown in this volume include the following: . Each town in New England, New York, and Wisconsin and each clsmor88.doc - Page 2 township in Michigan, New Jersey, and Pennsylvania that had no incorporated municipality as a subdivision and had either 25,000 inhabitants or more, or a population of 10,000 to 25,000 and a density of 1,000 persons or more per square mile. . Each county in States other than those indicated above that had no incorporated municipality within its boundary and had density of 1,000 persons or more per square mile. (Arlington County, Virginia, is the only county classified as urban under this rule.) . Each place in Hawaii with 10,000 or more population, as there are no incorporated cities in the State. Before 1964, places were classified as "urban" or "rural." The Technical Appendixes for earlier years discuss the previous classification system. State or country of birth Mortality statistics by State or country of birth (table 1-33) became available beginning with 1979. State or country of birth of a decedent is assigned to 1 of the 50 States or the District of Columbia; or to Puerto Rico, the Virgin Islands, or Guam--if specified on the death certificate. The place of birth is also tabulated for Canada, Cuba, Mexico, and for the Remainder of the World. Deaths for which information on State or country of birth was unknown, not stated, or not classifiable accounted for a small proportion of all deaths in 1988, about 0.6 percent. Early mortality reports published by the U.S. Bureau of the Census contained tables showing nativity of parents as well as nativity of decedent. Publication of these tables was discontinued in 1933. Mortality data showing nativity of decedent were again published in annual reports for 1939-41 and for 1950. Age The age recorded on the death record is the age at last birthday. With respect to the computation of death rates, the age classification used by the U.S. Bureau of the Census is also based on the age of the person in completed years. For computation of age-specific and age-adjusted death rates, deaths with age not stated are excluded. For life table computation, deaths with age not stated are distributed proportionately. Race For vital statistics in the United States in 1988, deaths are classified by race--white, black, American Indian, Chinese, Hawaiian, Japanese, Filipino, Other Asian or Pacific Islander, and Other. Mortality data for Filipino and Other Asian or Pacific Islander were shown for the first time in 1979. The white category includes, in addition to persons reported as white, those reported as Mexican, Puerto Rican, Cuban, and all other Caucasians. The American Indian category includes American, Alaskan, Canadian, Eskimo, and Aleut. If the racial entry on the death certificate indicates a mixture of clsmor88.doc - Page 3 Hawaiian and any other race, the entry is coded to Hawaiian. If the race is given as a mixture of white and any other race, the entry is coded to the appropriate other race. If a mixture of races other than white is given (except Hawaiian), the entry is coded to the first race listed. This procedure for coding the first race listed has been in use since 1969. Before 1969, if the entry for race was a mixture of black and any other race except Hawaiian, the entry was coded to black. Most of the tables in this volume, however, do not show data for this detailed classification by race. In about half of all the tables the divisions address white, all other (including black), and black separately. In other tables by race, where the main purpose is to isolate the major groups, the classifications are simply white and all other. Race not stated--For 1988 the number of death records for which race was unknown, not stated, or not classifiable was 4,094, or 0.2 percent of the total deaths. Death records with race entry not stated are assigned to a racial designation as follows: If the preceding record is coded white, the code assignment is made to white; if the code is other than white, the assignment is made to black. Before 1964 all records with race not stated were assigned to white except records of residents of New Jersey for 1962-64. New Jersey, 1962-64--New Jersey omitted the race item from its certificates of live birth, death, and fetal death in use in the beginning of 1962. The item was restored during the latter part of 1962. However, the certificate revision without the race item was used for most of 1962 as well as 1963. Therefore figures by race for 1962 and 1963 exclude New Jersey. For 1964, 6.8 percent of the death records in use for residents of New Jersey did not contain the race item. Adjustments made in vital statistics to take into account the omission of the race item in New Jersey for part of the certificates filed during 1962 through 1964 are described in the Technical Appendix of Vital Statistics of the United States for each of those data years. Hispanic origin Mortality statistics for the Hispanic-origin population were published in 1984 for the first time. They are based on information for those States and the District of Columbia that included items on the death certificate to identify Hispanic or ethnic origin of decedents. Data were obtained from the District of Columbia and the following 29 States: Alabama, Arizona, Arkansas, California, Colorado, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Maine, Mississippi, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York (including New York City), North Carolina, North Dakota, Ohio, Oregon, Rhode Island, Tennessee, Texas, Utah, Washington, and Wyoming. Hispanic mortality data were published for the time in 1984. Generally, the reporting States used items similar to one of two basic formats recommended by NCHS. The first format is open-ended to obtain the specific origin or descent of the decedent (for example, Italian, Mexican, Puerto Rican, English, and Cuban). The second format is directed specifically toward the Hispanic population and asks whether the decedent is of Spanish origin. If so, the specific origin--for example, Mexican, Puerto Rican, or Cuban--is to be indicated. For 1988, mortality data in tables 1-34 and 2-18 are based on deaths to residents of all 29 reporting States and the District of Columbia. In tables 1-35, 1-40, and 1-41 general mortality data for the Hispanic-origin population clsmor88.doc - Page 4 are based on deaths to residents of 26 reporting States and the District of Columbia whose data were at least 90 percent complete on a place-of- occurrence basis and considered to be sufficiently comparable to be used for analysis. The 26 States are as follows: Alabama, Arizona, Arkansas, California, Colorado, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Maine, Mississippi, Montana, Nebraska, New Jersey, New York (including New York City), North Carolina, North Dakota, Ohio, Oregon, Rhode Island, Texas, Utah, Washington, and Wyoming. Excluded from these tables are data for New Mexico because the format for the Hispanic item on the New Mexico death certificate departs sufficiently from that of other areas to result in noncomparable data. In addition, in tables 1-34 and 2-18 for New Mexico, no deaths are shown for the category "not stated" origin. Because of the way in which the item on the death certificate for New Mexico is worded, it was not possible to determine whether a blank entry represented a response of "non-Hispanic origin" or of "unknown origin." Accordingly, blank entries were coded to "non-Hispanic." Data for two other States--Nevada and Tennessee--are excluded from tables 1-35, 1-40, 1-41, because of the large proportion of deaths (in excess of 10 percent) occurring in these States for which Hispanic origin was not stated or was unknown. In tables 2-19, 2-20, 2-21, and 2-22, the reporting area is based on deaths to residents of 23 reporting States and the District of Columbia whose mortality data for all ages and whose live birth data were at least 90 percent complete on a place-of-occurrence basis and considered to be sufficiently comparable to be used for analysis. The 23 States are as follows: Alabama, Arizona, Arkansas, California, Colorado, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Maine, Mississippi, Montana, Nebraska, New Jersey, New York (including New York City), North Carolina, North Dakota, Ohio, Texas, Utah, and Washington. Data for New Mexico, Nevada, and Tennessee were excluded for the reasons stated above. Oregon and Rhode Island were excluded because their live birth certificates did not include an item to identify Hispanic or ethnic origin. Wyoming was excluded because of the large proportion of live births (in excess of 10 percent) for which Hispanic origin was not stated or was unknown. The 26 reporting States and the District of Columbia accounted for about 82 percent of the Hispanic population in the United States, including about 91 percent of the Mexican population, 79 percent of the Puerto Rican population, 35 percent of the Cuban population, and 72 percent of the "Other Hispanic" population (9). The 23 reporting States and the District of Columbia for which Hispanic infant mortality data are shown in this report accounted for about 81 percent of the Hispanic population, including about 90 percent of the Mexican population, 79 of the Puerto Rican population, 35 percent of the Cuban population, and 71 percent of the "Other Hispanic" population. Accordingly, caution should be exercised in generalizing mortality patterns from the reporting area to the Hispanic-origin population (especially Cubans) of the entire United States. For qualifications regarding infant mortality of the Hispanic-origin population, see "Infant deaths." Marital status Mortality statistics by marital status (table 1-32) were published in 1979 for the first time since 1961. (Previously they had been published in the annual volumes for the years 1949-51 and 1959-61.) Several reports analyzing mortality by marital status have been published, including the special study clsmor88.doc - Page 5 based on 1959-61 data (10). Reference to earlier reports is given in the appendix of part B of the 1959-61 special study. Mortality statistics by marital status are tabulated separately for never married, married, widowed, and divorced. Certificates in which the marriage is specified as being annulled are classified as never married. Where marital status is specified as separated or common-law marriage, it is classified as married. Of the 2,112,148 resident deaths 15 years of age and over in 1988, 12,603 certificates (0.6 percent) had marital status not stated. Place of death and status of decedent Mortality statistics by place of death were published in 1979 for the first time since 1958 (tables 1-29 and 1-30). In addition, mortality data were also available for the first time in 1979 for the status of decedent when death occurred in a hospital or medical center (table 1-29). These data were obtained from the following two items that appear on the U.S. Standard Certificate of Death: . Item 7c. Hospital or Other Institution--Name (If not in either, give street and number) . Item 7d. If Hosp. or Inst. Indicate DOA, OP/Emer. Rm., Inpatient (Specify) All of the States and the District of Columbia have item 7c (or its equivalent) on the death certificate. For all States and the District of Columbia in the Vital Statistics Cooperative Program, NCHS accepts the State definition, classification, or codes for hospitals, medical centers, or other institutions. Table 1-29 shows mortality data for the total of the following 44 States (including New York City) that have item 7d or its equivalent on their death certificates: Alabama Nebraska Alaska Nevada Arizona New Hampshire Arkansas New Jersey Colorado New Mexico Connecticut New York Florida North Carolina Georgia North Dakota Hawaii Ohio Idaho Oregon Illinois Pennsylvaina Indiana Rhode Island Iowa South Carolina Kansas South Dakota Kentucky Tennessee Louisiana Utah Maine Vermont Michigan Virginia Minnesota Washington clsmor88.doc - Page 6 Mississippi West Virginia Missouri Wisconsin Montana Wyoming Effective with data for 1980, the coding of place of death and status of decedent was changed. A new coding category was added: "Dead on arrival-hospital, clinic, medical center name not given." Deaths coded to this category are tabulated in table 1-29 as "Dead on arrival" and in table 1-30 as "Not in hospital or medical center. "Had the 1979 coding categories been used, these deaths would have been tabulated as "Place unknown." Mortality by month and date of death Deaths by month have been regularly tabulated and published in the annual volume for each year beginning with data year 1900. For 1988, deaths by month are shown in tables 1-20, 1-21, 1-24, 1-31, 2-12, 2-13, 2-14, and 3-9. Date of death was first published for data year 1972. In addition, unpublished data for selected causes by date of death for 1962 are available from NCHS. Numbers of deaths by date of death in this volume are shown in table 1-31 for the total number of deaths and for the number of deaths for the following three causes, for which the greatest interest in date of occurrence of death has been expressed: Motor vehicle accidents, Suicide, and Homicide and legal intervention. These data show the frequency distribution of deaths for the selected causes by day of week. They also make it possible to identify holidays with peak numbers of deaths from specified causes. Report of autopsy Before 1972, the last year for which autopsy data were tabulated was 1958. Beginning in 1972, all registration areas requested information on the death certificate as to whether autopsies were performed. For 1988, autopsies were reported on 251,095 death certificates, 11.6 percent of the total (table 1-28). Information as to whether the autopsy findings were used in determining the cause of death was tabulated for 1972-73 for all but nine registration areas and from 1974-77 for all but eight registration areas. The item "autopsy findings used" was deleted from the 1978 U.S. Standard Certificate of Death. For 10 of the cause-of-death categories shown in table 1-28, autopsies were reported as performed for 50 percent or more of all deaths (Shigellosis and amebiasis; Whooping cough; Meningococcal infection; Acute poliomyelitis; Pregnancy with abortive outcome; Other complications of pregnancy, childbirth, and the puerperium; Motor vehicle accidents; Suicide; Homicide and legal intervention; and All other external causes). There were four other categories for which 40 percent or more of the death certificates reported autopsies. Autopsies were reported for only 7.3 percent of the Major cardiovascular diseases. Cause of death Cause-of-death classification--Since 1949, cause-of-death statistics have been based on the underlying cause of death, which is defined as "(a) the clsmor88.doc - Page 7 disease or injury which initiated the train of events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury" (11). For each death the underlying cause is selected from an array of conditions reported in the medical certification section on the death certificate. This section provides a format for entering the causes of death in a sequential order. These conditions are translated into medical codes through use of the classification structure and the selection and modification rules contained in the applicable revision of the International Classification of Diseases (ICD) published by the World Health Organization (WHO). Selection rules provide guidance for systematically identifying the underlying cause of death. Modification rules are intended to improve the usefulness of mortality statistics by giving preference to certain classification categories over others and/or to consolidate two or more conditions on the certificate into a single classification category. As a statistical datum, the underlying cause of death is a simple, one-dimensional statistic; it is conceptually easy to understand and a well-accepted measure of mortality. It identifies the initiating cause of death and is therefore most useful to public health officials in developing measures to prevent the start of the chain of events leading to death. The rules for selecting the underlying cause of death are included with the ICD as a means of standardizing classification, which contributes toward comparability and uniformity in mortality medical statistics among countries. Tabulation lists--Beginning with data year 1979, the cause-of-death statistics published by the National Center for Health Statistics have been classified according to the Ninth Revision of the International Classification of Diseases (ICD-9) (11). In addition to specifying that the Classification be used, WHO also recommends how the data should be tabulated in order to promote international comparability. The recommended system for tabulating data in the Ninth Revision allows countries to construct their own mortality and morbidity tabulation lists from the rubrics of the WHO Basic Tabulation List as long as rubrics from the WHO mortality and morbidity lists, respectively, are included. This tabulation system for the Ninth Revision is more flexible than that of the Eighth Revision in which specific lists were recommended for tabulating mortality and morbidity data. The Basic Tabulation List (BTL) recommended under the Ninth Revision consists of 57 two-digit rubrics that add to the "all causes" total. Within each two-digit rubric, up to 9 three-digit rubrics numbered from 0 to 8 are identified, but these do not add to the total of the two-digit rubric. The two-digit rubrics of the BTL 01 through 46 provide for the tabulation of nonviolent deaths to ICD categories 001-799. Rubrics relating to chapter 17 (nature-of-injury causes 47 through 56) are not used by NCHS for selecting underlying cause of death; rather, preference is given to rubrics E47 through E56. The 57th two-digit rubric VO is the Supplementary Classification of Factors Influencing Health Status and Contact with Health Services and is not appropriate for the tabulation of mortality data. The WHO Mortality List, a subset of the titles contained in the BTL, consists of 50 rubrics which are a minimum for the national display of mortality data. Five lists of causes have been developed for tabulation and publication of mortality data in this volume: The Each-Cause List, List of 282 Selected Causes of Death, List of 72 Selected Causes of Death, List of 61 Selected Causes of Infant Death, and List of 34 Selected Causes of Death. These lists were designed to be as comparable as possible with the NCHS lists more clsmor88.doc - Page 8 recently in use under the Eighth Revision. However, complete comparability could not always be achieved. The Each-Cause List is made up of each three-digit category of the WHO Detailed List to which deaths may be validly assigned and most four-digit subcategories. The list is used for tabulation for the entire United States. The published Each-Cause table does not show the four-digit subcategories provided for Motor vehicle accidents (E810-E825); however, these subcategories, which identify persons injured, are shown in the accident tables of this report (section 5). Special fifth-digit subcategories are also used in the accident tables to identify place of accident when deaths from nontransport accidents are shown. These are not shown in the Each-Cause table. The List of 282 Selected Causes of Death is constructed from BTL rubrics 01-46 and E47-E56. Each of the 56 BTL two-digit titles can be obtained either directly or by combining titles in the List. The three-digit level of the BTL is modified more extensively. Where more detail was desired, categories not shown in the three-digit rubrics were added to the List of 282 Selected Causes of Death. Where less detail was needed, the three-digit rubrics were combined. Moreover, each of the 50 rubrics of the WHO Mortality List can be obtained from the List of 282 Selected Causes of Death. The List of 72 Selected Causes of Death was constructed by combining titles in the List of 282 Selected Causes of Death. It is used in tables published for the United States and each State, and for standard metropolitan statistical areas. The List of 61 Selected Causes of Infant Death shows more detailed titles for Congenital anomalies and Certain conditions originating in the perinatal period than any other list except the Each-Cause List. The List of 34 Selected Causes of Death was created by combining titles in the List of 72 Selected Causes. A table using this list is published for detailed geographic areas. Beginning with data for 1987, changes were made in these list to accommodate the introduction in the United States of new category numbers *042-*044 for Human immunodeficiency virus infection. The changes are described in the Technical Appendix From Vital Statistics of the United States, 1987. Effect of list revisions--The International Lists or adaptations of them, in use in this country since 1900, have been revised approximately every 10 years so that the disease classification may be consistent with advances in medical science and with changes in diagnostic practice. Each revision of the International Lists has produced some break in comparability of cause-of-death statistics. Cause-of-death statistics beginning with 1979 are classified by NCHS according to the ICD-9 (11). For a discussion of each of the classification used with death statistics since 1900, see Technical Appendix in Vital Statistics of the United States, 1979, Volume II, Mortality, Part A, Section 7, pages 9-14. A dual coding study was undertaken between the Ninth and the Eighth Revisions to measure the extent of discontinuity in cause-of-death statistics resulting from introducing the new Revision. An initial study for the List of 72 Selected Causes of Death and the List of 10 Selected Causes of Infant Death has been published (12). The List of 10 Selected Causes of Infant Death is a basic NCHS tabulation list not used in this volume but used for provisional data in the Monthly Vital Statistics Report, another NCHS publication. Comparability studies were also undertaken between the Eighth and Seventh, Seventh and Sixth, and Sixth and Fifth Revisions. For additional information clsmor88.doc - Page 9 these studies, again see the 1979 Technical Appendix. Significant coding changes during the Ninth Revision--Since the implementation of ICD-9 in the United States, effective with mortality data for 1979, several coding changes have been introduced. The more important changes will be discussed below. In early 1983, a change was made in the coding of acquired immunodeficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection, which affected data from 1981 to 1986. Also effective with data year 1981 was a coding change for poliomyelitis. For data year 1982, a change was made in the definition of child (which affects the classification of deaths to a number of categories, including Child battering and other maltreatment), and in guidelines for coding deaths to the category Child battering and other maltreatment (ICD No. E967). During the calendar year 1985 detailed instructions for coding motor vehicle accidents involving all-terrain vehicles (ATV's) were implemented to ensure consistency in coding these accidents. Effective with data year 1986, "primary" and "invasive" tumors, unspecified, were classified as "malignant"; these neoplasms had previously been classified to Neoplasms of unspecified nature (ICD-9 No. 239). Detailed discussion of these changes may be found in the Technical Appendix for previous volumes. Beginning with data for 1987, NCHS introduced new category numbers *042-*044 for classifying and coding Human immunodeficiency virus (HIV) infection, formerly referred to as human T-cell lymphotropic virus-III/ lymphadenopathy-associated-virus (HTLV-III/LAV) infection. The asterisk before the category numbers indicates that these codes are not part of the Ninth Revision. Also changed effective with data year 1987 were coding rules for the conditions "dehydration" and "disseminated intravascular coagulopathy". Detailed discussion of these changes may be found in the Technical Appendix for previous volumes. Coding in 1988--The rules and instructions used in coding the 1988 mortality medical data remained essentially the same as those used for the 1987 data except for minor content changes to the classification for Human immunodeficiency virus (HIV) infection that had initially been implemented for United States mortality data beginning in data year 1987. The basic structure of the HIV classification, the codes and category titles within the classification, and the manner in which the codes may be used remained unchanged for data year 1988. The 1988 modifications to the HIV classification included the addition of the following four conditions to the "Includes only" notes under several categories: isosporosis (007.2) under *042.0; diarrhea-noninfectious (558) and infections (009)-under *043.3; and lymphoid interstitial pneumonitis (516.8) under *043.3. In addition, several other terms were considered synonymous with HIV infection, and the following was added under the category *043.0: enlarged lymph nodes (785.6) swollen glands (785.6) Due to HIV infection Deaths classified to categories *042-*044 for 1988 are shown in Tables 1-36,1-37, 1-38, 1-39, 1-40, 1-41, 2-22, and 2023, and are also shown in the Each-Cause List in Table 1-23. Deaths classified to these categories are not shown separately in other tables showing cause-of-death data. clsmor88.doc - Page 10 Medical certification--The use of a standard classification list, although essential for State, regional, and international comparison, does not assure strict comparability of the tabulated figures. A high degree of comparability between areas could be attained only if all records of cause of death were reported with equal accuracy and completeness. The medical certification of cause of death can be made only by a qualified person, usually a physician, a medical examiner, or a coroner. Therefore, the reliability and accuracy of cause-of-death statistics are, to a large extent, governed by the ability of the certifier to make the proper diagnosis and by the care with which he or she records this information on the death certificate. A number of studies have been undertaken on the quality of medical certification on the death certificate. In general, these have been for relatively small samples and for limited geographic areas. A bibliography, prepared by NCHS (13), covering 128 references over a period of 23 years indicates that no definitive conclusions have been reached about the quality of medical certification on the death certificate. No country has a well-defined program for systematically assessing the quality of medical certifications reported on death certificates or for measuring the error effects on the levels and trends of cause-of-death statistics. One index of the quality of reporting causes of death is the proportion of death certificates coded to the Ninth Revision Chapter XVI symptoms, signs, and ill-defined conditions (ICD-9 Nos. 780-799). Although there are deaths for which it is not possible to determine the cause of death, this proportion indicates the care and consideration given to the certification by the medical certifier. It may also be used as a rough measure of the specificity of the medical diagnoses made by the certifier in various areas. In 1988, 1.4 percent of all reported deaths in the United States were assigned to ill-defined or unknown causes, a slight decrease from 1.5 in 1987. However, in 1988, this percentage varied among the States from 0.4 percent to 4.1 percent. While the percent for the United States for all ages combined has generally remained stable since 1979, declines have occurred for persons in age groups 55-64 years and 65-74 years, while increases have occurred for persons in age groups under 45 years. However, between 1987 and 1988, the percent decreased for almost all age groups. Automated selection of underlying cause of death--Beginning with data year 1968, NCHS began using a computer system for assigning the underlying cause of death. It has been used every year since to select the underlying cause of death. The system is called "Automated Classification of Medical Entities" (ACME). The ACME system applies the same rules for selecting the underlying cause as applied manually by a nosologist; however, under this system, the computer consistently applies the same criteria, thus eliminating intercoder variation in this step of the process. The ACME computer program requires the coding of all conditions shown on the medical certification. These codes are matched automatically against decision tables that consistently select the underlying cause of death for each record according to the international rules. The decision tables provide the comprehensive relationships between the conditions classified by ICD when applying the rules of selection and modification. clsmor88.doc - Page 11 Cause-of-death ranking--Cause-of-death ranking (except for infants) is based on the List of 72 Selected Causes of Death and the category Human immunodeficiency virus infection (HIV infection) (*042-*044); cause-of-death ranking for infants is based on the List of 61 Selected Causes of Infant Death and HIV infection. HIV infection was added to the list of rankable causes effective with data year 1987. The group titles Major cardiovascular diseases and Symptoms, signs, and ill-defined conditions from List of 72 Selected Causes of Death are not ranked; and Certain conditions originating in the perinatal period and Symptoms, signs, and ill-defined conditions from the List of 61 Selected Causes of Infant Death are not ranked. In addition, category titles that begin with the words "Other" or "All other" are not ranked to determine the leading causes of death. When one of the titles that represents a subtotal is ranked (such as Tuberculosis), its component parts (in this case, Tuberculosis of respiratory system and Other tuberculosis) are not ranked. Infant deaths Age--An infant death is defined as a death under 1 year of age. The term excludes fetal deaths. Infant deaths are usually divided into two categories according to age, neonatal and postneonatal. Neonatal deaths are those that occur during the first 27 days of life, and postneonatal deaths are those that occur between 28 days and 1 year of age. It has generally been believed that different factors influencing the child's survival predominate in these two periods: Factors associated with prenatal development, heredity, and the birth process were considered dominant in the neonatal period; and environmental factors, such as nutrition, hygiene, and accidents, were considered more important in the postneonatal period. Recently, however, the distinction between these two periods has blurred due in part to advances in neonatology, which have enabled more very small, premature infants to survive the neonatal period. Rates--Infant mortality rates shown in section 2 and section 8 are the most commonly used index for measuring the risk of dying during the first year of life; they are calculated by dividing the number of infant deaths in a calendar year by the number of live births registered for the same period and are presented as rates per 1,000 or per 100,000 live births. Infant mortality rates use the number of live births in the denominator to approximate the population at risk of dying before the first birthday. This measure is an approximation of the risk of dying in infancy because some of the live births will not have been exposed to a full year's risk of dying and some of the infants that die during a year will have been born in the previous year. The error introduced in the infant mortality rate by this inexactness is usually small, especially when the birth rate is relatively constant from year to year (17,18). Other sources of error in the infant mortality rate have been attributed to differences in applying the definitions for infant death and fetal death when registering the event (19,20). In contrast to infant mortality rates based on live births, infant death rates shown in section 1 are based on the estimated population under 1 year of age. Infant death rates, which appear in tabulations of age-specific death rates, are calculated by dividing the number of infant deaths in a calendar year by the estimated midyear population of persons under 1 year of age and are presented as rates per 100,000 population in this age group. Patterns and clsmor88.doc - Page 12 trends in the infant death rate may differ somewhat from those of the more commonly used "infant mortality rate" mainly because of differences in the nature of the denominator and in the time reference period. Whereas the population denominator for the infant death rate is estimated using data on births, infant deaths, and migration for the 12-month period of July through June, the denominator for the infant mortality rate is a count of births occurring during the 12 months of January through December. The difference in the time reference period can result in different trends between the two indices during periods when birth rates are markedly moving up or down markedly. The infant death rate is also subject to greater imprecision than is the infant mortality rate because of problems of enumerating and estimating the population under 1 year of age (20). Race--Infant mortality rates for specified races other than white or may be understated, based on results of studies in which race on the birth and death certificates for the same infant were compared (21). In the computation of regular race-specific infant mortality rates, the race item for the numerator comes from the death certificate, and for the denominator, from the birth certificate. Understatement may arise because of possible inconsistencies in reporting race between the death and birth certificates. Differences exist in the nature of reporting and processing race on these two vital records. With respect of reporting, race of parents is reported on the birth certificate by the mother at the time of delivery; whereas on the death certificate, race of the deceased infant is reported by the funeral director based on observation or on information supplied by an informant, such as a parent. With respect to processing, race of infant at birth is coded using coding rules that take account of the race of each parent (see the Technical Appendix in Vital Statistics of the United States, 1988, Volume I, Natality, section entitled "Race or national origin"); whereas race of infant decedent is coded directly from the race items as reported on the death certificate. There is a tendency for race of infant that was reported, for example, as American Indian or other specific race other than white at the time of death, resulting in understatement of infant mortality rates for smaller race groups. Estimates are made below of the degree of reporting bias in race-specific infant mortality rates by comparing two rates that differ in terms of the source of information about race of the decedent (22,23). The two rates are as follows: the birth cohort rate, based on data from the national linked birth and infant death data set, and the period rate, based on mortality and natality data for the same year(s). For the birth cohort, the race is that which is reported at the time of birth for the deceased infant and is the standard against which the race that is reported at the time of death is compared. The comparison of cohort and period rates is affected slightly by small differences in the events included in the numerators of the two rates. Thus, the numerator of the cohort rate is comprised of infant deaths to the cohort of infants born in a calendar year, whereas the numerator of the period rate is comprised of infant deaths that occur in the calendar year. Based on a comparison of infant mortality rates from the linked data set for the birth cohorts of 1983-85 with rates from the annual files for the 1983-85 period, bias in the rates for the two major race groups-the white and the black populations-is small. In contrast, period rates for the smaller race groups are estimated to be understated by between 21 and 44 percent, shown in Table A. clsmor88.doc - Page 13 Because of these differences in race-specific infant mortality rates, one should use, if possible, data from the nation linked birth and infant death data set to measure infant mortality for the smaller race groups. Hispanic origin--Infant mortality rates for the Hispanic-origin population are based on numbers of resident infant deaths reported to be of Hispanic origin (see section "Hispanic origin") and numbers of resident live births by Hispanic origin of mother for the 23 reporting States and the District of Columbia. In computing infant mortality rates, deaths and live births of unknown origin are not distributed among the specified Hispanic and non-Hispanic groups. Because for 1988 the percent of infant deaths of unknown origin was 6.7 percent and the percent of live births of unknown origin was 2.8 percent, infant mortality rates by specified Hispanic origin and race for non-Hispanic origin may be somewhat underestimated. Small numbers of infant deaths for specific Hispanic-origin groups can result in infant mortality rates subject to relatively large random variation (see section "Random variation in numbers of deaths, death rates, and mortality rates and ratios"). Tabulation list--Causes of death for infants are tabulated according to a list of causes that is different from the list of causes for the population of all ages, except for the Each Cause List. (See section "Cause-of-death classification.") California-Data on age at death for California, as shown in table 2-11, are biased in the categories 1-23 hours and 1 day because of processing errors that affected selected infants who died within 24 hours after birth, for each of the years 1985 through 1988. The degree of bias can be estimated by comparing the percents of infant deaths in these two age groups in the period before the error occurred, 1983-84, with the subsequent period, 1985-88, as follows: Age of infant 1983-84 1985-88 Percent distribution All Infants 100,000 100,000 1-23 hours 27.72 19.58 1 day 5.49 10.51 All other ages 66.80 69.91 Beginning with 1985 data, California provided NCHS with computer tapes of precoded mortality data through the Vital Statistics Cooperative Program (VSCP); whereas prior to 1985, data from the State of California were based on information coded by NCHS from copies of original death certificates. The effect of these errors on national data for the year 1985-88, shown in tables 2-2, 2-3, 2-12, and 2-16, is negligible. The problem has been identified and corrected for subsequent years. clsmor88.doc - Page 14