A script for success: taking SimWars from concept to completion

two approved regimens: double-dose of 500 IU at 28 and 34 weeks’ GA; and single-dose of 1500 IU at 28-weeks. Aim: To assess compliance and maintenance of circulating anti-D levels at delivery comparing singleand double-dose regimens of prophylaxis. A RCT (n = 280) compared a single 1500 IU dose of anti-D at 28-week to the current Australian regimen (28-and-34week 625 IU). Delivery antibody screening assessed circulating anti-D. Analyses were performed on intention to treat (ITT), and treatment received (TR). Statistical tests evaluated differences in compliance, detectability of residual anti-D, and maternal and neonatal outcomes. Multi variate logistic regression assessed factors contributing to undetectable anti-D at delivery. Demographic, obstetric and neonatal outcomes were similar between groups. No women sensitised during the study. Based on analyses by ITT and TR, the single-dose group had a higher proportion of undetectable anti-D at delivery (ITT OR 5.0; 45.2% vs. 14.2%, p < 0.001). Compliance was improved in the singledose group (77.1% vs. 60.7%, p < 0.001). Time elapsed since last dose, and third -trimester weight were significant predictors for undetectable anti-D at delivery. Multivariate regression indicated anti-D regimen group was not a significant predictor for undetectable anti-D at delivery. Based on individualized calculations of anti-D half-life, if Australia were to adopt a single dose regimen, there would be an estimated additional 15,641 women without adequate cover in the third-trimester.