To the Editor:—
We read with interest about the randomized controlled trial by Kotani et al. , suggesting that preoperative insertion of intradermal acupuncture may reduce postoperative pain. 1The authors concluded that the intervention “is easy to use, safe, and markedly improves postoperative analgesia.” We would like to raise a few methodological concerns, such as the double-blind terminology, credibility testing of the subject blinding, and the location of acupuncture points.
The definition of double-blind design varies (table 1). 2–5This study may or may not be double-blind, depending on which definition one follows. Considering the fact that it is not possible to mask the acupuncturist, their method is indeed of high quality. However, having seen clear discordance in the usage of the term “double-blind” in the reports, we believe it is more appropriate to use the phrase “subject- and assessor-blind.”6
The authors are to be applauded for testing the credibility of sham control in a pilot study in a separate group of 40 patients. However, the sample size was almost certainly not large enough to test the equivalence of the two different intervention modalities. In addition, we feel that it is not valid to assume that the credibility of subject blinding is same in all circumstances; it requires checking in each study. For this task, the investigators could have simply asked the participating patients which type of acupuncture they believed they received, either real, sham, or “do not know.”
Researchers are in general agreement that information given to the patient on random allocation of real or sham treatment influences subject's expectations. The authors “explained to each patient that insertion of intradermal needles is virtually painless and that they may or may not feel slight pain during insertion.” Yet they failed to report whether patients were informed of the possibility of receiving either of two modalities. This may confound subject blinding.
It is questionable whether 2.5 cm to the left and right of the T9–L3 spinal vertebrae are acupuncture points equivalent to BL18–BL24, because in a widely accepted acupuncture textbook, the cun or “body inch” is a measure that is individual for each person. 7The insertion of an intradermal needle on the location would be better understood as segmental dermatome stimulation.