Validity of congenital malformation diagnostic codes recorded in Québec's administrative databases

Purpose To assess the validity of the diagnostic codes of congenital malformations (CMs) recorded in two of Québec's administrative databases. Methods A cohort of pregnancies and infants born to asthmatic and non-asthmatic women in 1990―2002 was reconstructed using Québec's administrative databases. From this cohort, we selected 269 infants with a CM and 144 without CM born to asthmatic women, together with 284 and 138 infants, respectively, born to non-asthmatic women. The diagnoses of CMs recorded in the databases were compared with the diagnoses written by the physicians in the infants' medical charts. The positive predictive values (PPV) and negative predictive values (NPV) for all, major, and several specific CMs were estimated. Results The PPVs for all CMs and major CMs were 82.2% (95% confidence interval (CI): 78.5%―85.9%) and 78.1% (74.1%―82.1%), respectively, in the asthmatic group and were 79.2% (75.4%―83.1%) and 69.0% (64.6%―73.4%), respectively, in the non-asthmatic group. PPVs >80% were found for several specific CMs, including cardiac, cleft, and limb CMs in both groups. The NPV for any CM was 88.2% (95% CI: 85.1%―91.3%) in the asthmatic group and 94.2% (92.2%―96.2%) in the non-asthmatic group. Conclusions Québec's administrative databases are valid tools for epidemiological research of CMs. The results were similar between infants born to women with and without asthma.