From: Heterogeneity in pragmatic randomised trials: sources and management
Patients: Fetuses from women expected to deliver before 30 weeks of gestation Centres: 25 centres in seven countries Intervention: Delayed cord clamping Control: Immediate cord clamping Outcome: Composite outcome of death or major morbidity Design: Two parallel-group individually randomised trial | |
Sample size calculation: non-adherence | “The original sample was 1600 infants, yielding 90% power (two-sided P = 0.05) to detect an absolute difference in the incidence of the primary outcome of 8 percentage points between the two groups (30% in the immediate-clamping group vs. 22% in the delayed-clamping group; relative difference, 27%), with the assumption of 10% nonadherence. If the rate of nonadherence to the Intervention and loss to follow-up reached 20%, there was more than 80% power to detect this difference.” |
Subgroup analysis | “Tests for interaction were used to detect heterogeneity for the primary outcome in three prespecified subgroups: gestational age (<27 weeks vs. ≥27 weeks), sex, and method of delivery (cesarean section vs. vaginal delivery).” |