OBJECTIVE: To assess the credibility of subgroup claims in back pain randomised controlled trials. STUDY DESIGN AND SETTING: A sample of reports of back pain trials from 2000 to 2015 that provided a subgroup claim were included (n=38). Two reviewers independently assessed risk of bias and credibility of subgroup claims as well as the strength of the author's claim. The credibility of subgroup claims was assessed using a 10-criteria tool, and strength of the subgroup claims was assessed based on 7 criteria to categorise claims into reasonably strong claim of a definitive subgroup effect or a more cautious claim of a possible effect. RESULTS: A total of 91 claims of a subgroup effect were reported in the 38 included trials, of which 28 were considered strong claims of a definitive effect, and 63 were cautious claims of a possible effect. None of the subgroup claims met all 10 credibility criteria, and only 24% (22 claims) satisfied at least five criteria. The only criteria satisfied by more than 50% of the claims were if the subgroup variable was a characteristic measured at baseline, and whether the test of interaction was significant. All other criteria were satisfied by less than 30% of the claims. There was no association between the credibility of subgroup claims and the journal impact factor, risk of bias, sample size, or year of publication. CONCLUSION: The credibility of subgroup claims in back pain trials is usually low, irrespective of the strength of the authors' claim.
a1878-5921 (Electronic)