Abstract 214

Background: The primary outcome and the minimum detectable treatment difference (MDTD) in RCTs strongly affect sample size and the clinical utility of the study results. Aim: To perform a systematic review of primary outcomes in recent neonatal RCTs. Methods: Medline was searched for all neonatal RCTs, published since 1993 in six high-profile journals. Results: 129 reports were eligible for review. A primary outcome could not be identified in 32 (25%) reports. A continuous (i.e. surrogate) measure was the primary outcome in 48 (37%) trials. A binary outcome was short-term in 42 (33%) trials, and long-term in 7 (5%) trials. The median (minmax) MDTD was 50% (19-89%) in short-term trials, and 40% (30-67%) in long-term trials with primary binary outcomes. Conclusions: Most authors of recently published neonatal RCTs failed to specify a primary endpoint, or chose a continuous measure (e.g. oxygenation index) rather than a clinically important outcome event (e.g. death). Trials with a primary binary outcome tend to have a short duration of follow-up and unrealistically large minimum detectable treatment differences.