Lack of precision in neonatal death classifications based on the underlying causes of death stated on death certificates.

Abstract

Large-scale analyses of causes of neonatal deaths are usually based on death-certificate information. A new computer-based method has been introduced to define the cause of stillbirths and neonatal deaths in large amounts of material and to classify them according to two different models [Wigglesworth and Neonatal and Intrauterine death Classification according to (a)Etiology (NICE)]. The method is based on a combination of detailed information from health care registries and the death-certificate information. The present study aimed to compare these two classification models with a previously published method based solely on death certificate information [International Collaborative Effort (ICE)]. The study population comprised 2378 neonatal deaths in Sweden between 1987 and 1992. Cross-tabulation was made between the ICE classification and the other two classification models. In addition, case examples are presented in detail, exemplifying how classification errors arose. The ICE classification gives a rather low precision, notably for two important causes of death: asphyxia and immaturity. Among 328 infants dying from asphyxia according to computerized Wigglesworth classification, ICE classified 59% as asphyxia and 22% were labelled immaturity. When ICE classified the deaths as due to asphyxia, this was verified in only 50%. Among 792 infants dying from immaturity according to computerized Wigglesworth classification, 64% were classified as such by ICE. The findings cast doubts on the results of studies based exclusively on death-certificate information. Whenever possible in the analysis of neonatal deaths, death-certificate information should be supplemented with more detailed data. The computer-based method introduced here makes such analyses possible for large databases.