The effect of placebo in split‐scalp and whole‐head platelet‐rich plasma trials for androgenetic alopecia differs: Findings from a systematic review with quantitative evidence syntheses

Abstract

Background: Some studies have shown that platelet-rich plasma (PRP) improves androgenetic alopecia (AGA), while others do not. We determined whether the placebo effect significantly varies between split-scalp and whole-head trials on PRP monotherapy for AGA. Our rationale was based on the plausibility of PRP diffusing to the control (i.e., "placebo") side of split-scalp trials. This is not possible in whole-head studies. Methods:We systematically searched the literature for available data. Our choice of analyses and outcomes were determined by the available data.Results: Our endpoint was change in total hair density 6 months after baseline. Our regression showed that total hair density after 6 months was significantly (p < 0.05) higher in the placebo arm of split-scalp trials, compared to whole-head studies, by 37 hairs/cm 2 . Our one-arm meta-analyses showed that the pooled change in total hair density between the PRP side and placebo side in split-scalp studies was −3 hairs/ cm 2 (p = 0.37), that is, a slight decrease in hair density in the placebo side of the scalp.For whole-head studies, the corresponding difference in total hair density between patients receiving PRP and those on placebo was −30 hairs/cm 2 (p = 0.000017), that is, a much larger decrease in hair density. Patients in the placebo group in whole-head trials lost significantly more hair than in the placebo side of the split-head trials where hair loss was comparatively reduced -presumably because of PRP diffusing from the treatment side of the scalp. Conclusions:The association between design (i.e., split-scalp vs. whole-head) and outcome, in placebo arms of AGA trials on PRP monotherapy, had never been reported. This "design effect" could partly reconcile the incongruent conclusions across the PRP literature for AGA; furthermore, clinical guidelines can consider "design effect" when selecting evidence to base care practices on. K E Y W O R D S pattern baldness, placebo effect, platelet-rich plasma, regression analysis, split scalp | 1455 GUPTA And BAMIMORE How to cite this article: Gupta AK, Bamimore MA. The effect of placebo in split-scalp and whole-head rich plasma trials for androgenetic alopecia differs: Findings from a systematic review with quantitative evidence syntheses. J

Relative Effects of Minoxidil 5%, Platelet-Rich Plasma, and Microneedling in Pattern Hair Loss: A Systematic Review and Network Meta-Analysis

“…As per the patient (P), intervention (I), comparator (C), and outcome (O) framework for our study’s objective, we determined the relative efficacy of 5% minoxidil, PRP, and microneedling as stand-alone therapies or various combinations thereof (I/C) on adults (i.e., aged at least 18 years) with PHL (P) in terms of change in total hair density at 24 weeks (O). We chose this outcome as it is not only a common endpoint across AGA trials but is also a clinically relevant one [4, 7].…”

“…We used Rayyan for the coordination of our systematic review [8]. Our parameters for data extraction include authorship, year of publication, interventions’ details, sample size, patients’ characteristics (sex and disease severity), and design of treatment administration (whole-head vs. split-scalp); these variables were chosen a priori as findings from previous studies support that they can influence the efficacy of AGA therapies [7, 9].…”

“…We statistically adjusted for the effect of sex because dihydrotestosterone is implicated in PHL; moreover, efficacy of agents in AGA trials tends to be studied separately in men and women. Our adjustment for study design is based on the previous studies’ findings which support that PRP’s efficacy can be substantially influenced by whether the design of the trial was of a split-scalp or whole-head design [7]. Furthermore, we selected uniform priors for our Bayesian analyses – where we used 10,000 iterations, 1,000 burn-ins; Bayesian analyses were based on Markov chain Monte Carlo sampling.…”