Sample size
BPD
EVENT
The estimated incidence of the composite primary outcome of survival free of BPD is 50%, based on a review of data from the lead center (The Royal Women’s Hospital, Melbourne, Australia) and published studies enrolling extremely preterm infants. With a sample size of 1038 infants (519 in each group), the study has 90% power to detect a relative increase in survival free of BPD of 20% (an absolute increase of 10%), from the anticipated event rate of 50% in the control arm to 60% in the intervention (budesonide) arm, alpha error 0.05. To allow for up to 2% study withdrawals or losses to follow-up, PLUSS aimed to enroll a total of 1060 infants (530 in each arm).