True and placebo acupuncture
We decided to use a technique in the control group that did not
require transcutaneous penetration, thus avoiding neurophysi-
ological and neurochemical responses owing to the stimulation
of cutaneous receptors; the intervention and control groups
received treatments that were apparently identical: real acupunc-
ture plus medication versus placebo acupuncture plus medica-
tion. By supplying both groups with medication, we sought to
overcome possible ethical objections related to the role of the
control group in the study.
Blinding procedure
Although the standard treatment was given for 12 weeks, partici-
pants who dropped out of the study were mainly from the con-
trol group, and only six people were lost to the study because
their condition did not improve. To reinforce the blinding of the
groups we expanded the criteria for selection of study patients to
include the requirement that they should not have received pre-
vious acupuncture treatment; none of the participants lost to the
study made any reference to belonging to one or the other of the
two groups. Both the evaluation of the results and the statistical
analysis were carried out in a blind fashion. These factors
reinforce our belief that the blinding procedure applied was suc-
cessful.