Infrequent use of clinical trials registries in published systematic reviews in urology

Validity of systematic reviews may be affected by non-publication of statistically non-significant or unfavorable clinical trial results. One function of clinical trial registries is to make these non-published studies available and thereby reduce potential publication bias. We aim to assess the use of clinical trial registries in published systematic reviews in urology.

We identified all systematic reviews published in the five highest-impact general urology journals that publish original research between January 1 and December 31, 2017. Full-text analysis was performed to determine if protocols included searching clinical trial registries meeting WHO Registry Network criteria.

Of a total of 204 search results, 92 were included in the analysis as systematic reviews. The majority searched the MEDLINE (91, 98%), EMBASE (69, 75%), and Cochrane (49, 53%) databases. Based on published methods, only 16 (17%) systematic reviews searched any clinical trial registries: 14 (15%) ClinicalTrials.gov, 6 (6%) WHO International Clinical Trials Registry Platform, and 2 (2%) ISRCTN registry. Rates of searching clinical trial registries were low regardless of the journal: 8 of 34 (24%) in European Urology; 2 of 10 (20%) in BJU International; 3 of 17 (18%) in Urology; 2 of 18 (11%) in The Journal of Urology; and 1 of 13 (8%) in World Journal of Urology.

The majority of recently published systematic reviews in urology do not routinely search clinical trial registries. Inclusion of these registries can help identify unpublished trial data, which may improve the quality of systematic reviews by reducing publication bias.