Suggesting an Alternative to the Term “Double-blind”
The new term proposed by Park et al., “subject- and assessor-blind,” is reasonable. However, our study was well within the conventional meaning of double-blind, based on Jadad's criteria. 1Although a physician in charge of acupuncture treatment could not be blinded, patients participating in the study, the anesthesiologists providing intraoperative care, the physicians evaluating pain and morphine-related side effects, and the investigators measuring various biochemical mediators were fully blinded to the group assignment.
A more serious concern is whether the patients were really blinded. We accurately explained the nature of the study to each patient. We emphasized that insertion of these tiny intradermal needles is nearly painless. Furthermore, patients could not see the procedure because the needles were inserted on the backs while they were in the prone position. The needles were secured with opaque adhesive tape and remained in position for the entire study period. Because it is rarely possible for patients to detect insertion of these painless needles, it is thus unlikely that individuals were able to determine whether they were in the active treatment group. Placebo effects that are the most critical bias in acupuncture studies were thus minimal in our study. In fact, postoperative analgesic effects were supported by significant differences in various objective parameters including supplemental morphine requirement, incidence of side effects, and endocrinologic responses.
Our study would have been strengthened by contemporaneously asking patients to guess to which group they were assigned. However, the preliminary study reported in our paper demonstrated that 50–60% of the patients were unable to guess to which group they had been assigned; 20–30% guessed acupuncture, and the remaining 20% thought they were in the control group. These findings clearly indicate that patients were really blinded to treatment assignment.
Park et al. asked about our identification of acupoints in the bladder meridian. We agree that there are no established methods to identify acupoints or to detect individual differences of localization. 2Furthermore, gentle and strong acupuncture has a different effect. 3We thus defined a specific distance to minimize individual variety in the acupuncture procedure. Inaccurate needle placement would be a major concern had we failed to demonstrate a treatment effect. But in our case the technique was successful, suggesting appropriate positioning of the intradermal needles.