Systematic Review to Inform a World Health Organization (WHO) Clinical Practice Guideline: Benefits and Harms of Transcutaneous Electrical Nerve Stimulation (TENS) for Chronic Primary Low Back Pain in Adults.

Fourteen of the 17 trials were rated at high risk of bias, so the pooled estimates may be wrong in either direction. The subgroups were tiny, one to three trials each with 11 to 134 people per group, so the review cannot say whether TENS works better for any particular group, including older adults or people with or without leg pain. No trial followed anyone beyond about three months after treatment, so nothing here describes longer-term use. Only one trial reported harms, and it found none. That is far too little to conclude TENS is safe with prolonged use. Only 28 older adults were studied, in two small trials, and pain was essentially unchanged in them. The review did not search grey literature, which the authors acknowledge could bias the results toward larger effects. People with back surgery in the previous year, spinal fusion or disc replacement at any time, pregnancy, or a specific cause for their pain such as fracture, cancer or inflammatory disease were excluded, so the findings do not apply to them. No trials compared TENS with usual care, and none looked at fear avoidance, anxiety, self-efficacy or social participation including work.

The only funding declaration in the supplied text names the University of Zurich as the funder. No individual author competing-interest disclosures are given in the material provided.

Do not read the small drop in pain as proof that TENS works. It was under a point on a 0 to 10 scale, below the difference the review itself defined as clinically important. Every outcome was rated very low certainty evidence, and 14 of the 17 trials were at high risk of bias.