B. Bandelow et al., Application of a new statistical approach to evaluate a clinical trial with panic disorder patients, EUR ARCH PS, 249(1), 1999, pp. 21-27
In clinical trials in psychiatry, changes in severity are usually measured
with ordinal level scales which are applied repeatedly during the trial, sh
owing a constant decline in psychopathology scores as treatment leads to im
provement. Previous non-parametric tests for repeated measures in factorial
designs did not test the hypothesis that scale scores decrease constantly
during the trial. A recently developed "rank test for ordered alternatives
in a mixed model" was developed and applied to the data of a clinical trial
in panic disorder. Thirty-seven outpatients with panic disorder and agorap
hobia (PDA) were treated with imipramine (75-150 mg/day) in an 8-week open,
prospective trial. Patients with intercurrent agoraphobia were instructed
in practising self-exposure in their agoraphobic situations. The total scor
e on the Panic and Agoraphobia Scale, the Hamilton Anxiety Scale (HAMA) and
the Clinical Global Impression Scale (CGI) were used as the main efficacy
measures. The new rank test showed significant treatment results in all sca
les applied. Treatment results were excellent, as was shown by a decrease i
n the average Panic and Agoraphobia Scale severity scores from 28.9 (range
14-45) to 13.3 (range 0-37; rank statistic T-n = 6.7; p < 0.0001). The larg
est effect size r(w) of all clinician-rated scales was seen with the observ
er-rated version of the Panic and Agoraphobia Scale, although closely follo
wed by the CGI and the MAMA. Among the self-rated scales, the Panic and Ago
raphobia Scale also showed the largest effect size. All five subscores of t
he Panic and Agoraphobia Scale showed significant improvements. The highest
treatment effect sizes were seen in the "panic attacks" subscore, followed
by the "anticipatory anxiety" subscore. The new statistical test applied i
n this study, which has some advantages in comparison with previously appli
ed tests, is suitable for psychiatric treatment evaluations since it can al
so be applied in the case of discrete repeated measurements.