Table 4.
Characteristics of studies included in the verbal suggestion (itch) meta-analysis.
| Author | Year | N | Sample age | Percent female | Sensation induction method | Placebo manipulation | Rating scale | Risk of bias score | Comparison |
|---|---|---|---|---|---|---|---|---|---|
| Bartels12 | 2014 | 48 | 22.7 | 77% | Electrical | Sham electrode | 0-10 VAS | 4 | B |
| Darragh38 | 2015 | 48 | 22 | 78% | Histamine | Inert gel | 0-10 itch intensity scale | 1 | W |
| Peerdeman112 | 2015 | 59 | 21.8 | 71% | Histamine | Inert pill | 0-10 NRS | 3 | B |
| Skvortsova133 | 2018 | 54 | 22.1 | 100% | Histamine | Inert nasal spray | 0-10 NRS | 0 | B |
| van Laarhoven145 | 2011 | 36 | 21.8 | 100% | Histamine | Inert gel* | 0-10 VAS | 1 | B |
| Meeuwis99 | 2019 | 45 | 23.2 | 83% | Histamine | Inert gel | 0-10 NRS | 4 | W |
| Meeuwis98 | 2021 | 28 | 21.3 | 81% | Histamine | Sham patch | 0-10 NRS | 4 | W |
For studies using a within-subject comparison to measure the placebo effect, N is reported as the number of participants from the group in which the comparison was made. For studies using a between-subject comparison, N is reported as the number of participants from the placebo and control groups from which the comparison was made, or only the placebo condition in the case of within-subject comparisons.
No actual inert gel was applied, instead the histamine gel was used and participants were led to believe an additional medical gel was added. No outliers based on inspection of funnel plots (Supplementary material, http://links.lww.com/PAIN/B752) were detected in this analysis.
N, sample size; NRS, numeric rating scale; VAS, visual analogue scale.