Predictive value of pediatric thrombosis diagnoses in the Danish National Patient Registry

Data on the validity of pediatric thrombosis diagnoses are missing. We aimed to examine the predictive value of a diagnosis of venous and arterial thrombosis using the Danish National Patient Registry (DNPR). We identified all first-time diagnoses among children and adolescents (aged 0-18 years) between 1994 and 2006 in DNPR. In total, 1138 potential cases of thrombosis were identified; the medical records were retrieved for 1112 (97.7%) and the positive predictive value (PPV) computed. Overall, the diagnosis of thrombosis was verified in 598 of the 1112 cases, corresponding to a PPV of 53.7% (95% confidence interval [CI]: 50.8-56.7). Diagnoses from wards had the PPV of 62.5% (95% CI: 59.4-65.6). The predictive value of a thrombosis diagnosis from wards was age-dependent, with a higher PPV (77.4%, 95% CI: 68.7-84.7) in neonates (<28 days) and adolescents (15-18 years) (68.2%; 95% CI: 63.2-72.5)) than in children (28 days-14 years) (51.2%; (95% CI: 46.0-56.4)). The PPV of a thrombosis diagnosis was improved by restricting the analysis to diagnoses from wards, primary diagnoses, and admissions with a length of stay of three or more days. The results indicate that an interpretation of nonvalidated hospital discharge data for pediatric thrombosis in a registry like DNPR should be made with caution.