We would like to respond to the commentary with further understanding of the issue of potential statistical power in the analysis of our original finding. This further analysis has been planned to be carried out using the data from the wrinkle outcome because it has been contributed by the largest sample size with a dramatic effect size among all outcomes. Sequential analysis in this letter has been down with alpha 0.05 (type I error) and power of 0.80 (1—type II error) based on the O’Brien Fleming method. In addition to the common settings abovementioned, we chose a small effect size (SMD = 0.2) for avoiding underestimation in the optimal information size calculation and power analysis. The analysis was conducted using R via RStudio. The figure of sequential analysis shows that the cumulative effect of topical CM of stem cells on wrinkle outcome reaches statistical significance (z score of the end of blue line > 2), which is consistent with our original finding. Nevertheless, the information size of the outcome is insufficient (n = 118), which is lower than the required sample size (n = 1419). The observed power of the effects of topical CM of stem cells on the wrinkle outcome is only about 0.64, which is lower than the pre-defined or expected power of 0.80. Based on the fraction of information, although the observed z score of 3.232 for the cumulative effect surpasses 2, it does not surpass the monitoring boundary of 6.795 at the fraction (8.3%). Level of Evidence V This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Original languageEnglish
JournalAesthetic Plastic Surgery
Publication statusAccepted/In press - 2023


  • Conditioned medium
  • Exosomes
  • Meta-analysis
  • Nonsurgical resurfacing modalities
  • Stem cells
  • Systematic review
  • Trial sequential analysis

ASJC Scopus subject areas

  • Surgery


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