Comparison of registered and published primary outcomes in randomized controlled trials of gastroenterology and hepatology.

OBJECTIVES. The need for trial registration as well as the benefits it has brought for the transparency of medical research has been recognized for years. Trial registration has turned from an exception to a mandatory guideline in recent years. The present study aimed to examine the characteristics of registered randomized controlled trials (RCTs) in a sample of recently published gastroenterology RCTs, and to assess the consistency of registered and published primary outcome (PO) in RCTs. METHODS. Articles published in the top five "general and internal journals" and top five "gastroenterology and hepatology journals" categories between 2009 and 2012 were searched in PubMed. Basic characteristics and the registration information were identified and extracted from the included RCTs. PO consistency analysis was conducted to compare between the registered and published format. RESULTS. A total of 305 RCTs were included; among them 252 could be identified with a registration number. Nearly half of these RCTs were funded solely by industry (141/305, 46.3%). ClinicalTrials.gov was the most popular registry for these RCTs (214/252, 84.9%). A total of 155 RCTs were included in the PO consistency analysis. Among them, 22 (14.2%) RCTs had discrepancies between POs registered in the trial registry compared to the published article. CONCLUSIONS. Based on the results of the present study, selective outcome reporting of gastroenterology RCTs published in leading medical journals has been much improved over the past years. However, there might be a sampling bias to say that consistency of registered and published POs of gastroenterology RCTs has been better than before.