Retrospective Consent in a Neonatal Randomized Controlled Trial

BACKGROUND AND OBJECTIVES: The requirement for prospective consent in clinical trials in acute settings may result in samples unrepresentative of the study population, potentially altering study findings. However, using retrospective consent may raise ethical issues. We assessed whether using retrospective consent affected recruitment, participant characteristics, and outcomes within a randomized controlled trial. METHODS: We conducted a secondary analysis of a randomized trial, which compared nasal high flow (nHF) with nasal continuous positive airway pressure (CPAP) for primary respiratory support in preterm infants. In Era 1, all infants were consented prospectively; in Era 2, retrospective consent was available. We assessed inclusion rates of eligible infants, demographic data, and primary trial outcome (treatment failure within 72 hours). RESULTS: In Era 1, recruitment of eligible infants was lower than in Era 2: 111 of 220 (50%) versus 171 of 209 (82%), P < .001; intrapartum antibiotic administration was lower: 23 of 111 (21%) versus 84 of 165 (51%), P < .001; full courses of antenatal steroids were higher: 86 of 111 (78%) versus 103 of 170 (61%), P = .004; and more infants received pre-randomization CPAP: 77 of 111 (69%) versus 48 of 171 (28%), P < .001. In Era 1, nHF failure (15 of 56, 27%) and CPAP failure (14 of 55, 26%) rates were similar, P = .9. In Era 2, failure rates differed: 24 of 85 (28%) nHF infants versus 13 of 86 (15%) CPAP infants, P = .04. The χ2 interaction test was nonsignificant (P = .20). CONCLUSIONS: The use of retrospective consent resulted in greater recruitment and differences in risk factors between eras. Using retrospective consent altered the study sample, which may be more representative of the whole population. This may improve scientific validity but requires further ethical evaluation.