Letter to editor: the critical appraisal of “efficacy of licorice extract in the treatment of melasma: a randomized, double-blind, lacebo-controlled clinical trial”

This is a letter to editor criticizing the paper entitled “Efficacy of licorice extract in the treatment of melasma: A randomized, double-blind, placebo-controlled clinical trial”. We discuss some methodological points on external and internal validity of results. The paper suffers from lack of detailed information on sample size and power calculation to make sure generalisability of results to study population. The paper also did not report blinding procedure and placebo details. The results of the paper also suffer from multiplicity (multiple comparisons) and suitability of data analysis approach. It is recommended to apply either repeated measure ANOVA or a mixed model to consider correlation between repeated measure of outcomes and multiplicity problem.