Using Death Certificates to Characterize Sudden Infant Death Syndrome (SIDS): Opportunities and Limitations Carrie K. Shapiro-Mendoza, PhD, MPH, Shin Y. Kim, MPH, Susan Y. Chu, PhD, MSPH, Emily Kahn, PhD, MPH, and Robert N. Anderson, PhD Objective To examine cause-of-death terminology written on death certificates for sudden infant death syndrome (SIDS) and to determine the adequacy of this text data in more fully describing circumstances potentially contrib- uting to SIDS deaths. Study design With 2003 and 2004 US mortality files, we analyzed all deaths that were assigned the underlying cause-of-death code for SIDS (R95). With the terminology written on the death certificates, we grouped cases into SIDS-related cause-of-death subcategories and then assessed the percentage of cases in each subcategory with contributory or possibly causal factors described on the certificate. Results Of the 4408 SIDS-coded deaths, we subcategorized 67.2% as ‘‘SIDS’’ and 11.0% as ‘‘sudden unexplained (or unexpected) infant death.’’ The terms ‘‘probable SIDS’’ (2.8%) and ‘‘consistent with SIDS’’ (4.6%) were found less frequently. Of those death certificates that described additional factors, ‘‘bedsharing or unsafe sleep environment’’ was mentioned approximately 80% of the time. Most records (79.4%) did not mention any additional factors. Conclusion Our death certificate analysis of the cause-of-death terminology provided a unique opportunity to more accurately characterize SIDS-coded deaths. However, the death certificate was still limited in its ability to more fully describe the circumstances leading to SIDS death, indicating the need for a more comprehensive source of SIDS data, such as a case registry. (J Pediatr 2010;156:38-43). See related article, p 44 S udden infant death syndrome (SIDS), first defined in 1969, is now defined as ‘‘the sudden death of an infant <1 year of age, which remains unexplained after a thorough case investigation, including performance of a complete autopsy, ex- amination of the death scene, and review of the clinical history.’’ 1 Since 1973, when SIDS was first assigned an Interna- tional Classification of Diseases (ICD) code, US trends in SIDS have been monitored by counting deaths of infants whose death certificates indicated that SIDS was the underlying cause of the death. 2-4 Although the infant mortality rate attributable to SIDS has declined by >50% since recommendations for supine sleep position were established in the early 1990s, SIDS was still coded as the cause of nearly 2300 infant deaths in 2004. 5,6 Trends in SIDS rates since the late 1990s are difficult to interpret because of the wide variation in what defines a thorough case investigation, the quality of those investigations, and the comprehensiveness of the reported information. 7,8 Because SIDS and suffocation deaths cannot always be distinguished from one another with autopsy results alone, diagnosis often requires comprehensive evidence from a death scene investigation. 9 The underlying cause-of-death code in the ICD, 10th revision (ICD-10) that the National Center for Health Statistics (NCHS) generates depends on what the medical examiner, coroner, or other certifier reports on the death certificate, and there is substantial variation in how certifiers interpret and adhere to cause-of-death definitions. 10,11 In addition, there is complexity in the computer algorithms in the NCHS Mortality Medical Data System (an automated coding system). In brief, on the basis of ICD-10 coding rules, algorithms are applied to text reported on death certificates and used to code and generate an underlying cause of death. These coding rules were established to improve the usefulness and consistency of mortality statistics by giving preference to certain categories of death, by consolidating conditions, and by systematically selecting a single underlying cause from a reported sequence of conditions. 12 The rules are also used to select an underlying cause in cases in which the certifier has not appropriately spec- ified the underlying cause. For example, in cases in which SIDS is reported as caused by another condition or in which SIDS and another condition are re- ported on the same line, SIDS can be selected as the underlying cause even From the Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Division of Reproductive Health, Atlanta, GA (C.S-M., S.K., S.C., E.K.); and Centers for Disease Control and Prevention, National Center for Health Statistics, Hyattsville, MD (R.A.) The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Preven- tion. The authors declare no conflicts of interest. 0022-3476/$ - see front matter. Copyright Ó 2010 Mosby Inc. All rights reserved. 10.1016/j.jpeds.2009.07.017 ICD-10 International Statistical Classification of Diseases and Related Health Problems, 10th revision NCHS National Center for Health Statistics SIDS Sudden infant death syndrome SUID Sudden unexplained (or unexpected) infant death 38