Evaluating False Positives in Two Hospital Discharge Data Sets of the Birth Defects Monitoring Program

The principal goal in this study was to quantify false positives in the hospital discharge data of the Birth Defects Monitoring Program conducted by the Centers for Disease Control and Prevention. The two hospital data processing agencies which contribute data to the Birth Defects Monitoring Program, the Commission on Professional and Hospital Activities and the McDonnell Douglas Health Information Systems, had respective levels of false positives of 13.2 percent and 8.5 percent, levels which were statistically different from each other. These false positive levels should be considered minimal because these data bases do not include information on sick babies who may be transferred into or out of member hospitals, and who may have their initial diagnoses significantly modified. Potential correlates of false positives were evaluated, including hospital size, diagnostic certainty, race, sex, and insurance source. Two-thirds of all false positives were due to the miscoding of correctly diagnosed anomalies, and another quarter were clearly contradicted in notes easily available before the patients were discharged. The authors hope that this study of false positives will enhance the interpretation of the Birth Defects Monitoring Program data and lead to improved understanding of data collection and processing.