{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,27]],"date-time":"2026-04-27T11:25:45Z","timestamp":1777289145298,"version":"3.51.4"},"reference-count":33,"publisher":"Wiley","issue":"4","license":[{"start":{"date-parts":[[2022,2,7]],"date-time":"2022-02-07T00:00:00Z","timestamp":1644192000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J of Cosmetic Dermatology"],"published-print":{"date-parts":[[2022,4]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>Some studies have shown that platelet\u2010rich plasma (PRP) improves androgenetic alopecia (AGA), while others do not. We determined whether the placebo effect significantly varies between split\u2010scalp and whole\u2010head trials on PRP monotherapy for AGA. Our rationale was based on the plausibility of PRP diffusing to the control (i.e., \u201cplacebo\u201d) side of split\u2010scalp trials. This is not possible in whole\u2010head studies.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We systematically searched the literature for available data. Our choice of analyses and outcomes were determined by the available data.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Our endpoint was change in total hair density 6\u00a0months after baseline. Our regression showed that total hair density after 6\u00a0months was significantly (<jats:italic>p<\/jats:italic>\u00a0&lt;\u00a00.05) higher in the placebo arm of split\u2010scalp trials, compared to whole\u2010head studies, by 37\u00a0hairs\/cm<jats:sup>2<\/jats:sup>. Our one\u2010arm meta\u2010analyses showed that the pooled change in total hair density between the PRP side and placebo side in split\u2010scalp studies was \u22123\u00a0hairs\/cm<jats:sup>2<\/jats:sup> (<jats:italic>p\u00a0<\/jats:italic>=\u00a00.37), that is, a slight decrease in hair density in the placebo side of the scalp. For whole\u2010head studies, the corresponding difference in total hair density between patients receiving PRP and those on placebo was \u221230\u00a0hairs\/cm<jats:sup>2<\/jats:sup> (<jats:italic>p\u00a0<\/jats:italic>=\u00a00.000017), that is, a much larger decrease in hair density. Patients in the placebo group in whole\u2010head trials lost significantly more hair than in the placebo side of the split\u2010head trials where hair loss was comparatively reduced \u2013 presumably because of PRP diffusing from the treatment side of the scalp.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>The association between design (i.e., split\u2010scalp vs. whole\u2010head) and outcome, in placebo arms of AGA trials on PRP monotherapy, had never been reported. This \u201cdesign effect\u201d could partly reconcile the incongruent conclusions across the PRP literature for AGA; furthermore, clinical guidelines can consider \u201cdesign effect\u201d when selecting evidence to base care practices on.<\/jats:p><\/jats:sec>","DOI":"10.1111\/jocd.14813","type":"journal-article","created":{"date-parts":[[2022,1,31]],"date-time":"2022-01-31T20:29:25Z","timestamp":1643660965000},"page":"1454-1463","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["The effect of placebo in split\u2010scalp and whole\u2010head platelet\u2010rich plasma trials for androgenetic alopecia differs: Findings from a systematic review with quantitative evidence syntheses"],"prefix":"10.1111","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8664-7723","authenticated-orcid":false,"given":"Aditya Kumar","family":"Gupta","sequence":"first","affiliation":[{"name":"Mediprobe Research Inc.  London Ontario Canada"},{"name":"Division of Dermatology Department of Medicine University of Toronto School of Medicine  Toronto Ontario Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mary A.","family":"Bamimore","sequence":"additional","affiliation":[{"name":"Mediprobe Research Inc.  London Ontario 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