Objectives: Many randomized clinical trials (RCTs) are labelled efficacy and safety while due consideration for power is provided only for efficacy outcomes. This in turn necessitates a discussion of the inadequacy of sample size (type II error) for identifying harm. This is particularly important in RCTs of TNF inhibitors as harm related to these agents is still a matter of debate.
Methods: PubMed was searched for all RCTs published examining TNF inhibitors in RA, PsA and AS. Only original study reports were surveyed for whether: (i) they were labelled as efficacy, safety or both; (ii) the methods sections included safety as a primary or secondary end point; (iii) power calculations were adequately explained; (iv) statistical tests of significance were given for harm; and finally (v) any discussion of type II error for harm was present.
Results: Of the 34 articles surveyed, 24 (71%) were labelled as efficacy and safety. Among these, 23 (96%) did not include safety as a formal primary or secondary end point. In only 2/24 (8%) power calculations were given for safety. Finally, in only 3/22 (14%) any discussion about the inadequate sample size (type II error) for detecting harm could be found.
Conclusions: Most reports of RCTs of TNF inhibitors in rheumatological diseases are inappropriately labelled as addressing efficacy and safety. Their lack of power in detecting harm is not adequately discussed, either.