Antal 2010

Methods	Cross‐over RCT
Participants	Country of study: Germany Setting: laboratory setting Condition: mixed chronic pain, neuropathic and non‐neuropathic Prior management details: therapy‐resistant n = 23, 10 in parallel (6 active, 4 sham), 13 crossed over Age: active‐only group 28‐70 years, sham‐only group 50‐70 years, cross‐over group 41‐70 years Duration of symptoms: chronic 1.5‐25 years (mean 7.4) Gender distribution: 6 M, 17 F
Interventions	Stimulation type: tDCS Stimulation parameters: intensity 1 mA, 35 cm2 electrodes, duration 20 min Stimulation location: anode ‐ L M1 hand area, cathode right supraorbital Number of treatments: x 5, daily Control type: sham tDCS
Outcomes	Primary: pain VAS 0‐10; VAS anchors 0 = no pain, 10 = the worst pain possible When taken: x 3, daily ‐ averaged for daily pain Secondary: none relevant
Notes	Funding: government funding COI: none declared
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomization was performed using the order of entrance into the study." Comment:  may not be truly random from description
Allocation concealment (selection bias)	Unclear risk	Comment: not mentioned though unlikely given the randomisation technique. This is a potentially significant source of bias given that only the parallel results were used in this review due to high levels of attrition after the first phase
Adequate blinding of participants?	Low risk	Comment: see above
Adequate blinding of assessors?	Low risk	Comment: 1 mA intensity and operator blinded Quote: "The stimulators were coded using a five letter code, programmed by one of the department members who otherwise did not participate in the study. Therefore neither the investigator not the patient knew the type of the stimulation"
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: the high level of dropout renders the cross‐over results at high risk of bias. This is less of an issue where only the parallel results from the first phase were used ‐ first‐phase data only used in the analysis
Selective reporting (reporting bias)	Low risk	Comment: while not all outcomes at all time points were included in the study report the authors have provided all requested data
Free from carry‐over effects?	Low risk	Comment: participants were excluded if pain had not returned to normal. This, however, represents a threat with regard to attrition bias
Study Size	High risk	Comment: < 50 participants per treatment arm
Study duration	Unclear risk	Comment: ≥ 2 weeks but < 8 weeks' follow‐up
Other bias	Low risk	Comment: no other sources of bias detected