Secular trends in the impact factors of SLE publications over a 45-year period—a systematic review

Objective: We assessed publication bias in the field of systemic lupus erythematosus (SLE) by conducting a search of randomized, controlled trials (RCTs) on SLE therapies that had been published over the past 45 years. Our aim was to assess a potential publication bias by determining whether RCTs reporting positive results, RCTs with placebo arms, biologics RCTs, and industry-funded RCTs are more likely to be published in journals with higher impact factors (IFs). Methods: We conducted a systematic review of all RCTs registered in PubMed between 1 January 1975 and 1 November 2016. Each RCT was classified as having a positive result (PR) or a negative result (NR). The IF of each journal was determined for the year of publication. Results: Our search yielded 233 relevant RCTs. There was no significant difference in IFs between studies with NRs and those with PRs or between studies that were financially supported by commercial companies compared to studies that were not. However, there was a significant correlation between sample size and the journal’s IF. Conclusions: IF scores of RCTs in the field of SLE are influenced by sample size and not biased by either a tendency to report PRs or by being funded by pharmaceutical companies or any other commercial sources.