Objective Physiological Outcome
Objective and Subjective Outcomes
At each of the 12 visits, spirometry was used to obtain a baseline measurement of FEV1, after which patients received the intervention for that particular visit (as randomly assigned within the four visits of that block of visits). Spirometry was then repeated every 20 minutes for 2 hours. Also at each visit, patients were asked to score any perceived improvements in asthma symptoms on a visual-analogue scale, with scores ranging from 0 (no improvement) to 10 (complete improvement), and were also asked whether they thought they had received a genuine therapy or placebo (to assess blinding). These subjective responses were then converted to percent improvement in FEV1 during the 2 hours by multiplying each score by 10.
Statistical Analysis
Drug and placebo effects were assessed by means of repeated-measures analysis of variance. If significant main effects were found, we compared each intervention with the use of two-tailed, paired t-tests. We used a Bonferroni correction to control type I error, and only those effects with P values of less than 0.008 were considered to be significant. (See the Supplementary Appendix for details.) The magnitudes of the effects were assessed with the use of Cohen’s d statistic, which provides a measure of the differences in the mean values of changes in symptom severity between groups in relation to the pooled standard deviation.
Patients
Objective Physiological Outcome
Percent Change in Maximum Forced Expiratory Volume in 1 Second (FEV1) with Each of the Four Interventions. shows the mean physiological responses to each intervention (albuterol inhaler, placebo inhaler, sham acupuncture, and no intervention) across the three study visits. At the initial screening visit, the mean (±SE) percent improvement in FEV1 in response to open-label albuterol was 21.9±1.6%, and all patients had an improvement in FEV1 of at least 12%. During the double-blind test series, the mean percent improvement in FEV1 was 20.1±1.6% with inhaled albuterol, as compared with 7.5±1.0% with inhaled placebo, 7.3±0.8% with sham acupuncture, and 7.1±0.8% with the no-intervention control. There were no significant differences between the three inactive interventions, none of which resulted in the degree of improvement observed with active albuterol. The difference in drug effect between the albuterol inhaler and the placebo inhaler, as indexed by the difference in mean percent improvement in FEV1, was significant (P<0.001) and large (d=1.48). In contrast, the placebo effects did not differ significantly between the two placebo interventions and the no-intervention control (P=0.65 for the comparison of placebo inhaler with no intervention, and P=0.75 for the comparison of sham acupuncture with no intervention). In addition, the sizes of these effects were negligible (d=0.07 for placebo inhaler and d=0.04 for sham acupuncture). With the use of the standard definition of treatment response (≥12% improvement in FEV1 13), patients assigned to the active albuterol inhaler had a response 77% of the time, whereas patients assigned to the placebo inhaler, those assigned to sham acupuncture, and those assigned to no intervention had a response 24%, 20%, and 18% of the time, respectively.