Chapter 2 – Meta-analysis 35 that have cited them and should potentially be included in the metaanalysis. When necessary, authors of studies were contacted in order to provide full-text articles that were not accessible online. Any disagreements regarding study inclusion were resolved by consultation with a third author (K.J.P.). Data extraction One author (J.S.B.) used a standardized form to independently extract data from the included studies to derive data for analyses. Another author (M.A.T.) checked 25% of extracted values for accuracy. Extracted information included details of the intervention such as the learning method used, the control condition, study population, sensation type, pain/itch rating data, type of cutaneous stimulation (e.g., heat pain, pressure pain), type of outcome expected (i.e., placebo or nocebo), information for quality assessment, and outcome data for meta-analysis (e.g., sample size, pain/itch rating means and standard deviations). Doubts regarding data-extraction were resolved through discussion with a third review author (K.J.P.). Missing data were requested directly from the study authors. When there was no response from authors, but data could be extracted from published figures, this was done using WebPlotDigitizer version 4.4 (Rohatgi, 2020). Risk of bias Risk of bias (RoB) was assessed and checked by two authors (M.A.T. and J.S.B.) using the method developed by Marcuzzi and colleagues specifically for quantitative sensory testing studies 23. This method assesses whether the sample was clearly described and was representative of the population, whether the somatosensory assessment
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