Congenital malformations: agreement between diagnostic codes in an administrative database and mothers' reports

The validity of epidemiologic research on congenital malformations conducted using administrative databases relies heavily on the quality of diagnostic information. The goal of this study was to validate the diagnostic codes for major congenital malformations (MCMs) recorded in a medical service claims database against mother's report obtained by questionnaire.

Using the Quebec Pregnancy Registry, we mailed a questionnaire to women who gave birth to a baby with an MCM and to a random sample of mothers whose infants did not have any malformation. We reviewed each infant's database record for a diagnostic code for MCM, which we then compared with the corresponding mother's report.

Among the 3142 mother-infant pairs there was 60% agreement regarding the presence or absence of an MCM; for 456 babies, both sources reported the presence of an MCM. For 90% of these infants the two sources of information agreed with respect to the type of malformation.

Overall, mothers reported fewer infants with MCM than were recorded in the database; among those for whom both sources of information indicated the presence of an MCM, a very high proportion of diagnostic codes accorded with the mother's description of the specific type of malformation.