Spin and fragility in randomised controlled trials in the anaesthesia literature: a systematic review

Background: Given variable frequency of misleading reports and the potential for spin (a way of describing results that can mislead readers) to influence interpretation of randomised controlled trials (RCTs), we have undertaken a spin reassessment. We evaluated the quality of recent literature in anaesthesia journals by assessing the presence of spin and calculating the fragility index.

Methods: This systematic review of randomised trials was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. We searched via PubMed® from January 1, 2019 to January 1, 2021 to identify all RCTs published in one of the 20 anaesthesia journals with the highest journal impact factors during this time. Four pairs of reviewers assessed articles independently for eligibility using a piloted electronic data extraction form. They assessed the presence of spin in statistically negative RCTs and calculated the fragility index for statistically positive RCTs.

Results: Of the 802 screened records, 162 (20%) articles were analysed for spin, and 65 (8%) trials were analysed for fragility index. For the statistically negative studies, 66 articles (40%) presented spin; 89% of these occurrences of spin were described in the conclusion of the abstract. The primary type of spin was the highlight of secondary outcomes (67%). For statistically positive trials, the median fragility index was 4 [1-8].

Conclusions: This systematic review showed that 40% of statistically negative trials in high-impact anaesthesia journals could mislead readers. For statistically positive RCTs, the results relied on few subjects, with a median fragility index of 4 [1-8]. Efforts must be continued to reduce spin and fragility in the medical literature.