Blood transfusion is frequently used as an indicator of severe maternal morbidity during pregnancy. However, few studies have examined its validity in population perinatal databases.
We linked a perinatal database from British Columbia, Canada, with the province’s Central Transfusion Registry for 2004–2015 deliveries. Using the Central Transfusion Registry records for red blood cell transfusion as the gold standard, we calculated the sensitivity, specificity, positive predictive value, and negative predictive value of the perinatal database variable for red blood cell transfusion, overall and by transfusion risk factor status. We used multivariable logistic regression to examine whether outcome misclassification altered the odds ratios for different transfusion risk factors.
Among 473,688 deliveries, 4,033 (8.5 per 1,000) had a red blood cell transfusion according to the Central Transfusion Registry. The sensitivity of the perinatal database transfusion variable was 72.3 [95% confidence interval (CI) = 72.2, 72.4]. Sensitivity differed according to the presence of many transfusion risk factors (e.g., 84.9% vs. 72.2% in deliveries with versus without uterine rupture). Odds ratios associated with some transfusion risk factors were exaggerated when the perinatal database transfusion variable was used to define the outcome instead of the Central Transfusion Registry variable, but 95% confidence intervals for these estimates overlapped.
Blood transfusion was documented with reasonable sensitivity in this large population perinatal database. However, validity varied according to risk factor status. Our findings enable researchers to better account for outcome misclassification in studies of obstetrical transfusion risk factors.