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Is TENS purely a placebo effect? A controlled study on chronic low back pain
Marchand S, Charest J, Li J, Chenard JR, Lavignolle B, Laurencelle L
Pain 1993 Jul;54(1):99-106
clinical trial
5/10 [Eligibility criteria: Yes; Random allocation: Yes; Concealed allocation: No; Baseline comparability: Yes; Blind subjects: No; Blind therapists: No; Blind assessors: No; Adequate follow-up: Yes; Intention-to-treat analysis: No; Between-group comparisons: Yes; Point estimates and variability: Yes. Note: Eligibility criteria item does not contribute to total score] *This score has been confirmed*

Although high-frequency low-intensity trascutaneous electric nerve stimulation (TENS) has been extensively used to relieve low back pain, experimental studies of its effectiveness have yielded contradictory findings mainly due to methodological problems in pain evaluation and placebo control. In the present study, separate visual analog scales (VAS) were used to measure the sensory-discriminative and motivational-affective components of low back pain. Forty-two subjects were randomly assigned to 1 of 3 groups: TENS, placebo-TENS, and no treatment (control). In order to measure the short-tem effect of TENS, VAS pain ratings were taken before and after each treatment session. Also, to measure long effects, patients rated their pain at home every 2 h throughout a 3-day period before and 1 week, 3 months and 6 months after thre treatment sessions. In comparing the pain evaluations made immediately before and after each treatment session, TENS and placebo-TENS significantly reduced both the intensity and unpleasantness of chronic low back pain. TENS was significantly more efficient than placebo-TENS in reducing pain intensity but not pain unpleasantness. TENS also produced a significant additive effect over repetitive treatment sessions for pain intensity and relative pain unpleasantness. This additive effect was not found for placebo-TENS. When evaluated at home, pain intensity was significantly reduced more by TENS than placebo-TENS 1 week after the end of treatment, but not 3 months and 6 months later. At home evaluation of pain unpleasantness in the TENS group was never different from the placebo-TENS group. These results suggest that TENS reduces both the sensory-discriminative and motivational-affective components of low back pain in the short term but that much of the reduction in the affective component may be a placebo effect. We conclude that TENS should be used as a short-tem analgesic procedure in a multidisciplinary program for low back pain rather than as an exclusive or long-term treatment.

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