Comment on “Effects of remimazolam versus dexmedetomidine on recovery after transcatheter aortic valve replacement under monitored anesthesia care: a propensity score-matched, non-inferiority study”

Dear Editor,

We read with great interest the article “Effects of remimazolam versus dexmedetomidine on recovery after transcatheter aortic valve replacement under monitored anesthesia care: a propensity score-matched, non-inferiority study” [1] and wish to reflect our views on the design of the study.

Kim et al. [1] reported their study as a “propensity score-matched, non-inferiority study.” Notably, a non-inferiority study is conducted to prove that a new or reference treatment is not inferior to the existing one [2] and thus is a prospective interventional study. However, the study conducted by Kim et al. [1] was a retrospective, observational study. Furthermore, before commencing a non-inferiority study, the non-inferiority margin should be calculated, and the sample size should be determined based on a previously published superiority study (preferably one that compares the existing treatment with a placebo) [2]. Importantly, all these details should be stated during trial registration. Hence, unfortunately, the current study cannot be considered a “non-inferiority study.”

In this regard, we would like to highlight a statement made by Hong and Lee [3] in their recently published article describing the key points and challenges of this type of study: “As the sample size in a study is determined by the noninferiority margin, it should be predetermined based on strict criteria and cannot be modified based on the results after the study is completed.”