Validating Obstructive Genitourinary Defects in an Environment of Potential Overdiagnosing

Area of Science:

• Pediatric Health Surveillance
• Birth Defect Epidemiology
• Medical Informatics

Background:

• The Department of Defense Birth and Infant Health Registry monitors birth defects in military families.
• A 30% increase in obstructive genitourinary defects (OGDs) was noted in the Registry from 2009-2011.
• A validation study was conducted to investigate the source of this observed increase.

Purpose of the Study:

• To validate the accuracy of obstructive genitourinary defect (OGD) diagnoses within the Department of Defense Birth and Infant Health Registry.
• To assess the positive predictive value of specific ICD-9-CM codes used for OGD case identification.
• To inform future case definitions for birth defect surveillance.

Main Methods:

• A random sample of 30 infants diagnosed with OGDs (ICD-9-CM codes 753.2 or 753.6) from a specific military hospital (2010-2011) was selected.
• Physician review of electronic medical records was performed to confirm true OGD cases.
• Positive predictive value and 95% confidence intervals were calculated.

Main Results:

• Physician review confirmed only 10% (95% CI, 2%-27%) of the sampled OGD diagnoses as true cases.
• Approximately 97% of infants in the sample were assigned the less severe ICD-9-CM code 753.2.
• The majority of identified OGD cases were false positives, likely due to the inclusion of less severe diagnoses.

Conclusions:

• The findings support the 2014 modifications to the National Birth Defects Prevention Network (NBDPN) OGD case definition.
• Excluding ICD-9-CM code 753.2 from reporting is recommended as it represents a less severe OGD diagnosis.
• Exclusion of less severe codes can reduce false positive cases and improve surveillance accuracy.