Comparison of noninferiority margins reported in protocols and publications showed incomplete and inconsistent reporting.

OBJECTIVES: To compare noninferiority margins defined in study protocols and trial registry records with margins reported in subsequent publications.

STUDY DESIGN AND SETTING: Comparison of protocols of noninferiority trials submitted 2001 to 2005 to ethics committees in Switzerland and The Netherlands with corresponding publications and registry records. We searched MEDLINE via PubMed, the Cochrane Controlled Trials Register (Cochrane Library issue 01/2012), and Google Scholar in September 2013 to identify published reports, and the International Clinical Trials Registry Platform of the World Health Organization in March 2013 to identify registry records. Two readers recorded the noninferiority margin and other data using a standardized data-abstraction form.

RESULTS: The margin was identical in study protocol and publication in 43 (80%) of 54 pairs of study protocols and articles. In the remaining pairs, reporting was inconsistent (five pairs, 9%), or the noninferiority margin was either not reported in the publication (five pairs, 9%) or not defined in the study protocol (one pair). The confidence interval or the exact P-value required to judge whether the result was compatible with noninferior, inferior, or superior efficacy was reported in 43 (80%) publications. Complete and consistent reporting of both noninferiority margin and confidence interval (or exact P-value) was present in 39 (72%) protocol-publication pairs. Twenty-nine trials (54%) were registered in trial registries, but only one registry record included the noninferiority margin.

CONCLUSION: The reporting of noninferiority margins was incomplete and inconsistent with study protocols in a substantial proportion of published trials, and margins were rarely reported in trial registries.