Relapse rates also differed among sites (Table 4). The effect of site on outcome was, therefore, assessed separately for each period, assuming a proportional hazard for time to relapse. The hazard for relapse was modeled as a function of pattern, treatment, and site, including all 2- and 3-factor interactions. The Cox proportional hazards analysis did not show a significant site-by-pattern-by-treatment interaction for any period: for the 12-week analysis, Wald test score=5.02, df=1, and P<.29; for the 26-week analysis, Wald testscore=0.04, df=1, and P<.95; and for the 50-week analysis, Wald test score=0, df=1, and P≤.99). We also tested whether patients with placebo patterns had different outcomes depending on whether they had an early initial response or a late and nonpersistent initial response. The Kaplan-Meier survival analysis was not significant for any of the periods (log-rank test score=0.09, df=1, P<.77 for weeks 19-26; log-rank test score=0.14, df=1, P<.71 for weeks 26-50; and log-rank test score=1.21, df=1, P<.28 for weeks 50-62). Because sex, site, or placebo pattern subtype were not significant in the analyses described, subsequent analyses did not adjust for these factors.