Villamar 2013

Methods	Cross‐over RCT
Participants	Country of study: USA Setting: laboratory Condition: fibromyalgia Prior management details: pain refractory to common analgesics and muscle relaxants n = 18 randomised of which 17 allocated Age mean (SD): 50.3 (8.5) years Duration of symptoms (years) mean (SD): 10.7 (6.8) Gender distribution: 15 F, 3 M
Interventions	Stimulation type: HD‐tDCS Stimulation parameters: intensity 2 mA, duration 20 min, anodal/cathodal/sham 4 x 1‐ring configuration Stimulation location: L M1 Number of treatments: x 1 per condition Control type: sham tDCS
Outcomes	Primary: pain visual numerical scale; 0 = complete absence of pain, 10 = worst pain imaginable When taken: baseline, immediately poststimulation, 30 min poststimulation Secondary: adapted QoL scale for persons with chronic illness (7 points: 1 = terrible, 7 = delighted)
Notes	COI: no declaration made Sources of support: no declaration made
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "the order of stimulation was counterbalanced and randomly assigned for each individual" Comment: method of randomisation not specified but less likely to introduce bias in a cross‐over design
Adequate blinding of participants?	Unclear risk	Comment: there is evidence that participant blinding of tDCS may be inadequate at 2 mA intensity (see Assessment of risk of bias in included studies)
Adequate blinding of assessors?	Unclear risk	Comment: there is evidence that participant blinding of tDCS may be inadequate at 2 mA intensity (see Assessment of risk of bias in included studies)
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: only 1 loss to follow‐up and multiple imputation used
Selective reporting (reporting bias)	Low risk	Comment: primary outcomes reported in full
Free from carry‐over effects?	Low risk	Comment: 7‐day washout periods observed. Data similar at baseline
Study Size	High risk	Comment: < 50 participants per treatment arm
Study duration	High risk	Comment: < 2 weeks' follow‐up
Other bias	Low risk	Comment: no other bias detected