Reanalysis of data suggests that effect is not a placebo effect

EDITOR—Irnich et al reported that acupuncture was superior to massage though not to sham acupuncture for neck pain.1 This suggests that acupuncture is effective but that this is due to a placebo effect.

The statistical method used (comparing improvements in pain between groups with pairwise t tests) is of questionable efficiency. Firstly, regression analysis including baseline score as a covariate has greater statistical power than comparison of change. 2 3 Secondly, each pairwise comparison in a three group trial ignores one third of the patients; such comparisons are thus underpowered when compared with regression modelling of all data.

Analysis of change scores, such as that reported, favours the group with worse baseline pain scores (in this case, the group …