Performance of an autopsy is essential in attributing an unexplained death to sudden infant death syndrome (SIDS) * (1). Geographic variations in SIDS cases have been attributed to differences in postmortem protocols and interpretations of autopsy information (2), which also relate to variations in the types of certifiers and their training in cause-of-death determinations. An investigation of a cluster of 20 deaths attributed to SIDS in a county in Washington during 1980-1994 indicated that autopsies had been performed in only 14 (70%) cases. By excluding deaths that did not meet the case definition because autopsies were not performed, the rate for this county was reduced by 30%. In Washington, suspected SIDS cases must be investigated and certified by a medical examiner, coroner, or prosecuting attorney acting as a coroner (referred to in this report as investigative certifiers). The causes of death that are not within the legal jurisdiction of the investigative certifier system may be certified by any other physician (referred to in this report as medical doctor, not investigative certifier). This report examines the percentage of deaths attributed to SIDS in Washington that were followed by an autopsy during 1980-1994 by county, the type of certifier, and the type of county investigative certifier system (3). The findings indicate that many deaths in Washington counties are attributed to SIDS despite the lack of an autopsy and that all suspected SIDS cases are not being referred to investigative certifiers.

Potential cases of SIDS were identified by searching birth- and death-certificate data contained on public-use data tapes compiled by the Washington State Center for Health Statistics. Cases were defined as deaths among infants who were aged less than 365 days at the time of death attributed to SIDS (International Classification of Diseases, Ninth Revision, code 798.0) and who were born to Washington residents. Numbers of live-born infants were used as the denominator for calculating death rates. Rates of deaths attributed to SIDS were calculated by dividing the number of SIDS cases by the number of live-born infants during 1980-1994 for each county. Death certificate files included information about the county of residence, whether an autopsy was performed, and the type of certifier of each death.

During 1990-1994, county-specific rates for SIDS, as recorded on the death certificate, ranged from 57 to 652 cases per 100,000 live-born infants. The percentage of autopsies performed following these deaths ranged from 50% to 100% and were greater than 80% in all but four counties. However, when death rates were based only on deaths that were followed by an autopsy, rates for SIDS decreased as much as 33% in some counties. Among deaths that were certified by an investigative certifier, the percentage that were followed by an autopsy ranged from 57% to 100% and was greater than 80% in all but four counties.

Overall, the percentage of deaths attributed to SIDS that were followed by an autopsy was 94% during 1980-1984, 95% during 1985-1989, and 98% during 1990-1994. In general, the percentage of autopsies was higher in counties with a medical examiner than in those with a coroner system, and in counties with investigative certifiers than in those with medical doctors who were not investigative certifiers (Table_1). During 1985-1989 and 1990-1994, the percentage of autopsies increased substantially (83% to 95%) among medical doctors who certified deaths in counties with a coroner system and among medical doctors who certified deaths in counties with a prosecuting attorney serving as the coroner (75% to 95%). However, the proportion of SIDS cases certified by medical doctors decreased from 40% (357) during 1980-1994 to 21% (157) during 1990-1994.

Reported by: J VanEenwyk, Office of Epidemiology, Washington State Dept of Health. Office of Surveillance and Analysis, National Center for Chronic Disease Prevention and Health Promotion; State Br, Div of Applied Public Health Training (proposed), Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: The findings in this report indicate that because reviews of deaths in Washington by investigative certifiers are neither centralized nor routine, the diagnosis of SIDS varies among counties. In Washington, certification of infant deaths that lack an apparent cause is within the legal jurisdiction of the investigative certifiers system. The type of investigative certifier system varies by county and includes appointed medical examiners (four counties, in which three are forensic pathologists), elected coroners (17; three are medical doctors), and prosecuting attorneys serving as the coroner (18) (3). In 18 states, investigator certifier systems are mixed medical examiner/coroner systems; systems in 11 states include only coroners, and in 21 states and the District of Columbia only medical examiners (3). Because a statewide, centralized investigative certifier system exists in only 25 states (3), postmortem protocols for deaths attributed to SIDS probably vary in other states.

Infants with suspected cases of SIDS should have an autopsy performed by a forensic pathologist who has specialized training in cause-of-death determinations, and the autopsy should include histologic and toxicologic examinations. The quality and interpretation of postmortem information varies (4), in part, because many investigative certifier systems do not have a written protocol that specifies the criteria to be used to diagnose SIDS (5). The College of American Pathologists has recommended that nosologic classifications be refined to reflect the amount of available diagnostic information (6). This would enable analysis of SIDS to distinguish between a thoroughly informed diagnosis of SIDS (based on a complete autopsy and a death scene investigation) and a diagnosis of "presumed SIDS," which lacks quality diagnostic information (6).

Accurate data are needed to evaluate temporal trends and geographic and demographic variations in SIDS rates and to better understand the causes of SIDS. A centralized investigative certifiers system would improve the standardization of diagnostic and postmortem protocols among county coroners and medical examiners. In addition, this centralization would enhance the quality of data for investigation of SIDS and other causes of death that are difficult to diagnose and are within the legal jurisdiction of investigative certifiers. County-specific data will be used to increase awareness in Washington counties of the importance of referral of suspected SIDS cases to an investigative certifier and of an autopsy for diagnosis of SIDS.

References

1. CDC. Sudden infant death syndrome -- United States, 1980-88. MMWR 1992; 41:515-7.

2. Helweg-Larsen K, Knudsen LB, Gregersen M, Simonsen J. Sudden infant death syndrome (SIDS) in Denmark: evaluation of the increasing incidence of registered SIDS in the period 1972 to 1983 and results of a prospective study in 1987 through 1988. Pediatrics 1992;89:855-9.

3. Combs DL, Parrish RG, Ing R. Death investigation systems in the United States and Canada, 1995. Atlanta: US Department of Health and Human Services, Public Health Service, CDC, National Center for Environmental Health, 1996.

4. Keeling JW, Golding J, Sutton B. Identification of cases of sudden infant death syndrome from death certificates. J Epidemiol Community Health 1985;39:148-51.

5. Kaplan JA, Hanzlick R. The diagnosis of sudden infant death syndrome: medical examiner practices and attitudes. Proceedings of the American Academy of Sciences 1995:33:135-6.

6. Hanzlick R, ed. The medical cause of death manual: instructions for writing cause of death statements for deaths due to natural causes, 1994. Skokie, Illinois: College of American Pathologists, 1994.

The sudden death of an infant aged less than 1 year that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.

TABLE 1. Number and percentage of deaths attributed to sudden infant death
syndrome (SIDS) * and percentage of deaths attributed to SIDS that were followed by
an autopsy, by time period, + type of county investigative certifier system, and type of
certifier & -- Washington, 1980-1994
===================================================================================================
Time period/                Deaths attributed to SIDS
 Type of certifier system/  -------------------------   Percentage
 Type of certifier                No.       (%)         autopsied
------------------------------------------------------------------
1980-1984
  Medical examiner
    Investigative certifier       224       (25)            97%
    Medical doctor                238       (27)           100%
  Coroner
    Investigative certifier       240       (27)            93%
    Medical doctor                 98       (11)            83%
  Prosecuting attorney
    Investigative certifier        58       ( 7)            84%
    Medical doctor                 21       ( 2)            90%

1985-1989
  Medical examiner
    Investigative certifier       288       (31)           100%
    Medical doctor                210       (23)           100%
  Coroner
    Investigative certifier       265       (28)           95%
    Medical doctor                 78       ( 8)            83%
  Prosecuting attorney
    Investigative certifier        71       ( 8)            90%
    Medical doctor                 16       ( 2)            75%

1990-1994
  Medical examiner
    Investigative certifier       291       (39)           100%
    Medical doctor                 93       (12)            98%
  Coroner
    Investigative certifier       248       (33)            96%
    Medical doctor                 44       ( 6)            95%
  Prosecuting attorney
    Investigative certifier        50       ( 7)            94%
    Medical doctor                 20       ( 3)            95%
------------------------------------------------------------------
* International Classification of Diseases, Ninth Revision, code 798.0
+ SIDS cases with an unknown county of death or certified by "other" certifiers (e.g., osteopaths
  and chiropractors) were excluded (1980-1984, n=45; 1985-1989, n=27; and 1990-1994, n=28).
& Investigative certifier (i.e., medical examiner, elected coroner, or prosecuting attorney) or
  medical doctor (who is not an investigative certifier).
===================================================================================================

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