Mediprobe Research Inc., London, Ontario, Canada.
Division of Dermatology, Department of Medicine, University of Toronto School of Medicine, Toronto, Ontario, Canada.
J Cosmet Dermatol. 2022 Apr;21(4):1454-1463. doi: 10.1111/jocd.14813. Epub 2022 Feb 7.
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.
We systematically searched the literature for available data. Our choice of analyses and outcomes were determined by the available data.
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 . 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 (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 (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.
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.
一些研究表明，富血小板血浆（PRP）可改善雄激素性脱发（AGA），而另一些则不然。我们旨在确定 PRP 单药治疗 AGA 的头皮分割试验和全头皮试验的安慰剂效应是否存在显著差异。我们的推理基于 PRP 扩散到头皮分割试验对照（即“安慰剂”）侧的合理性。这在全头皮研究中是不可能的。
我们系统地检索了文献中的可用数据。我们的分析和结果选择取决于可用数据。
我们的终点是基线后 6 个月的总发密度变化。我们的回归显示，与全头皮研究相比，头皮分割试验安慰剂组 6 个月后的总发密度显著（p<0.05）高 37 根/平方厘米。我们的单臂荟萃分析显示，头皮分割试验 PRP 侧与安慰剂侧之间总发密度的总变化为-3 根/平方厘米（p=0.37），即头皮安慰剂侧的发密度略有下降。对于全头皮研究，接受 PRP 和安慰剂的患者之间总发密度的相应差异为-30 根/平方厘米（p=0.000017），即发密度下降更大。全头皮试验安慰剂组的患者脱发明显多于头皮分割试验安慰剂侧，头皮分割试验安慰剂侧的脱发相对减少-可能是因为 PRP 从头皮治疗侧扩散。
PRP 单药治疗 AGA 试验安慰剂组的设计（即头皮分割与全头皮）与结局之间的关联以前从未报道过。这种“设计效应”可以部分解释 AGA 中 PRP 文献的不一致结论；此外，临床指南在选择证据来指导护理实践时可以考虑“设计效应”。
