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we thank you for your recent Editorial (1) that gives a balanced and useful view of the use of anti-interleukin1 agents for the treatment of recurrent pericarditis (2). As it is common, the authors conclude that “however, larger RCT data are required for further validation of the efficacy and safety of these novel medications in the treatment of recurrent pericarditis.” Here there is a technical issue, that sometimes may be not well appreciated. One of the first step in planning a RCT is to calculate the sample size. The point is that RCT that will randomize subjects to anti-IL 1 agents vs placebo will never be large, and will always include a small number of subjects, as compared to sample sizes common in other fields of cardiology, simply given the large treatment effect; for this reason is not ethical to randomize higher number of subjects. The calculated sample sizes are relatively small only due to the expected extremely high efficacy: e.g. the per protocol calculated sample sizes were 20 subjects in the AIRTRIP trial (3) and 56 in the RHAPSOSY trial (4). In practice we will never have “large” RCT on this topic, because these agents are expected to be so effective that the calculated sample sizes will be always small.
1. Anthony C, Collier P. Anti-interleukin-1 for recurrent pericarditis; maybe a fix (but prior studies do not really mix). Heart. 2021 May 10:heartjnl-2021-319282. doi: 10.1136/heartjnl-2021-319282. Online ahead of print.
2. Imazio M, Andreis A, Piroli F, et al. Anti-interleukin1 agents for the treatment of recurrent pericarditis: a systematic review and meta-analysis.Heart 2021. doi:10.1136/heartjnl-2020-318869. [Epub ahead of print: 18 Mar 2021].
3. Brucato A, Imazio M, Gattorno M, et al. Effect of Anakinra on recurrent pericarditis among patients with colchicine resistance and corticosteroid dependence: the AIRTRIP randomized clinical trial. JAMA 2016;316:1906–12.
4. Klein AL, Imazio M, Cremer P, et al. Phase 3 trial of interleukin-1 trap rilonacept in recurrent pericarditis. N Engl J Med 2021;384:31–41.