Lofgren 2009.

Methods	Type of study: randomised, controlled, cross‐over. Condition and number of participants randomised: fibromyalgia (1990 American College of Rheumatology Criteria) 32 randomised. Groups: TENS (n = 29 analysed), superficial warmth (n = 28 analysed).
Participants	Demographics: n = 32, age (mean ± SD): 41 ± 8.3 years, all women. Setting: University Hospital, Stockholm, Sweden. Inclusion: age 18‐60 years. Exclusion: drug misuse, serious psychiatric disease, previous experience of using TENS to alleviate musculoskeletal pain. Withdrawal/dropouts: 2 participants for reasons not related to study.
Interventions	Where applied: hospital. Applied by: participants but a physiotherapist instructed the participants where to apply the electrodes. Instructions to participants: how and where to apply the TENS electrodes. Duration of intervention: 21 days, no washout period between interventions. TENS Waveform: not reported. Frequency: 80 Hz. Pulse duration: not reported. Pulse amplitude/intensity: strong but not unpleasant level. Electrodes: 4 electrodes, 3 × 8 cm. Electrode placement: at sites of pain. Duration and frequency of Rx: daily at least 30 minutes per session, use as often as needed for 3 weeks before transfer to thermal stimulator with no washout period. Device/manufacturer: Cefar Primo stimulator (Cefar AB, Malmö, Sweden). Superficial warmth Portable thermal electrical stimulation, 40 ± 2 ºC, 4 electrodes (3 × 8 cm), on painful sites, use for 45 minutes to 2 hours per day for 3 weeks.
Outcomes	Duration of follow‐up: during intervention period only; 21 days. No post‐intervention follow‐up. Pain outcome: 0‐100 NRS (no pain to worst imaginable) before and after each treatment session. Pain diaries to report how long pain reduction lasted. Change of ≥ 20 points (NRS) considered a responder. Fibromyalgia Impact Questionnaire. Type of analysis: ITT and per‐protocol. Statistical analysis: between group differences (Mann Whitney test). Adverse effects: not reported.
Notes	Country of origin: Sweden. Conflict of interest: not reported. Sponsorship: Swedish Rheumatism Association, Department of Rehabilitation Medicine, Danderyd University Hospital and the Division of Rehabilitation Medicine.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Study reported as randomised but method not described.
Allocation concealment (selection bias)	Unclear risk	Not described; study was cross‐over design.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants: not blind. Care providers administering TENS: not blind. Physiotherapist administered both treatments.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome assessors: not blind (outcome assessor was the physiotherapist administering treatments).
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	2/32 participants dropped out of the study for reasons "unrelated to treatment." In addition, 1 of the remaining 30 participants did not complete TENS intervention and 2 participants did not complete the warmth intervention. An ITT and per‐protocol analysis performed although how dropout data were handled was unclear.
Selective reporting (reporting bias)	Unclear risk	No protocol registered or published. Prespecified primary outcomes for pain reported.
Sample size	High risk	< 50 participants per treatment arm.
Other bias	Unclear risk	Conflict of interest: not reported. Sponsorship: Swedish Rheumatism Association, the Department of Rehabilitation Medicine, Danderyd University Hospital and the Division of Rehabilitation Medicine. Study stopped early: no. Parity of groups at baseline: yes ‐ cross‐over study with no significant differences in pain measures at pre‐intervention time points, i.e. 'no carry‐over effects detected.' Timing of outcome measurement between groups: identical. Comparability of cointerventions between groups: not reported. Funding declarations: Swedish Rheumatism Association, the Department of Rehabilitation Medicine, Danderyd University Hospital and the Division of Rehabilitation Medicine.