Acupuncture for knee

We believe AiM readers will be interested to learn of the factors that led to negative reporting of the positive study by Hinman et al on acupuncture for knee osteoarthritis (OA) pain. The study showed the effects of acupuncture to be significantly superior to no acupuncture and consistent with the best current evidence, but the authors actually reported: ‘Our findings do not support acupuncture for these patients’. Patients with OA knee pain are suffering the commonest cause of pain and disability in elderly people. More than half have inadequate pain relief. They face ‘a choice between ineffective paracetamol, non-steroidal drugs that can harm the heart, (kidneys) and gastrointestinal tract, gels that scarcely work, physiotherapy, opioids that cause dependency and lose effectiveness, arthroscopic washouts that do nothing or surgery’. They deserve a fuller, more considered answer to their question: should they try acupuncture? The neat part of the Zelen design that Hinman et al used was that the control group, who were not given acupuncture, were not even aware that their pain scores were used in a trial of acupuncture so disappointment could not influence their scores, as was claimed for other studies. This ‘no acupuncture’ group was compared with acupuncture (manual) and with sham laser (and with real laser, which is not considered here, to keep things simple). The problems started with the trialists’ choice of the threshold minimum clinically important difference (MCID) to estimate sample size. They chose a value based on one chosen by six self-styled ‘expert’ physicians, namely a 35% fall in baseline pain score (1.8/sample mean baseline 5.1). This is equivalent to an effect size (ES) of 0.6, calculated using their assumed baseline SD of 30 (the actual SD was 21, giving a higher threshold ES of 0.86). A different figure for MCID was generated by 192 patients with OA, who registered improvement scores as well as changes in pain. This showed a more modest MCID, equivalent to an ES of 0.39 (shown in figure 1). The National Institute for Health and Care Excellence (NICE) did not regard any value for MCID as valid and chose a generic value of 0.5 (see figure 1). Hinman et al chose a high threshold and also failed to discuss the effect that alternative threshold MCID values would have on the interpretation of their findings. We also note that the MCID for any treatment should be chosen to take account of acceptability, safety and cost-effectiveness, which would argue for a lower threshold for acupuncture for knee pain. Next, Hinman et al applied this ‘clinically important’ difference to a ‘clinically irrelevant’ comparison— acupuncture versus sham laser. Sham laser is not an available therapy. The only reason for comparing acupuncture with sham would be to estimate