Objective: To validate the discharge diagnoses of venous thromboembolism during pregnancy and postpartum, we examined the positive predictive value (PPV) of venous thromboembolic (VTE) discharge diagnoses associated with pregnancy or puerperium based on 311 cases registered in a Danish population-based hospital-discharge registry.
Study design and setting: Medical records and hospital discharge summaries were retrieved and reviewed using a standardized form. Standard and pregnancy-specific codes were used for 147 (49%) and 153 (51%) cases, respectively.
Results: The overall PPV of the selected codes was 87.3% (95% confidence interval [CI]: 83.0-90.9). When focusing on confirmed VTE events in relation to the pregnancy, the overall PPV was 79.3% (95% CI: 74.3-83.8).
Conclusion: The overall PPVs of pregnancy-related VTE diagnoses were moderate to high. The predictive values varied substantially between the individual codes, however, and not all the registered VTE events occurred in relation to pregnancy. Thus, use of unvalidated registry-based pregnancy-related VTE diagnoses for epidemiological research may lead to biased results.