Scientometric measures of prospectively registered clinical trials over time: A comparison of IRCT and ClinicalTrials.gov

Iranian Registry of Clinical Trials (IRCT) started as a primary registry in 2008. We examined the characteristics and scientometric measures of prospectively registered clinical trials in IRCT over time and compared them with that of ClinicalTrials.gov  

We selected eligible trial records between 2008 and 2016 from the IRCT database. We assessed their characteristics and the journal metrics of ensuing outputs over the study period and compared our findings with the corresponding information from ClinicalTrials.gov reported by Magdalena Zwierzyna et al. and a random sample of trials registered with this registry.  We used the chi-square test for comparison of proportions and Mann-Whitney U test for comparison of medians.  P-value <0.05 was considered statistically significant. Statistical analyses were performed using IBM SPSS Statistics V.22.

1751 prospectively registered clinical trials were eligible for analysis, of which 1526 (87%) had parallel-group design, 1541 (88%) reported to be randomized, 753 (43%) used double-blinding design, 485 (%27.7) had sample size more than 100, 1313 (75%) completed within a year, 1539 (87.9%) were single centered and 1529 (87.3%) exclusively used public money. Comparison with ClinicalTrials.gov showed that they are less likely to have multiple centers, funded by private sectors, continue beyond one year; and more likely to be randomized, double-blind and get published as a paper. The sample sizes were similar. Journal scientometric measures remained constant over the study period for both databases but were higher in ClinicalTrials.gov (median SJR=1.67, IQR=1.1-3.23) compared with IRCT (median SJR=0.58, IQR=0.34-0.91).

Our findings suggest that clinical trials registered in IRCT are predominantly investigator-initiated studies with acceptable methodological features and high publication rate albeit in journals with substantially lower scientometric measures compared with that of ClinicalTrials.gov. Journal metric indices remained constant despite an increase in the number of registrations in IRCT.