Portilla 2013

Methods	Cross‐over RCT
Participants	Country of study: USA Setting: laboratory Condition: postburn neuropathic pain Prior management details: varied n = 3 Age range: 34‐52 years Duration of symptoms: > 6 months Gender distribution: 2 F, 1 M
Interventions	Stimulation type: tDCS Stimulation parameters: intensity 2 mA, duration 20 min Stimulation location: M1 contralateral to most painful side Number of treatments: 1 per condition Control type: sham tDCS (switched off after 30 s stimulation)
Outcomes	Primary: pain VAS; 0 = "no pain", 10 = "worst pain ever felt" When taken: before and after stimulation Secondary: none relevant
Notes	COI: study authors declared no COI Sources of support: departmentally funded
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "subjects were randomized to either active tDCS or sham stimulation." Comment: method of randomisation not specified but less critical in 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: all 3 participants completed study
Selective reporting (reporting bias)	High risk	Comment: no numeric data provided for pain outcomes
Free from carry‐over effects?	Unclear risk	Comment: 1‐week washout observed but no data reported for pain outcome so unable to assess this issue
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