Michael E Thase1, Klaus G Larsen, Sidney H Kennedy. 1. University of Pennsylvania School of Medicine, and Philadelphia Veterans Affairs Medical Center, Philadelphia, Pennsylvania, USA. USA. thase@mail.med.upenn.edu
Abstract
BACKGROUND: There is controversy about the implications of relatively small average drug-placebo differences observed in randomised controlled trials of antidepressant medications. AIMS: To investigate whether efficacy is better understood as a large effect in a subgroup of patients. METHOD: The mixture model was used to identify patient subgroups (patients benefiting or not benefiting from treatment) to directly model the skewness ofMontgomery-Åsberg Depression Rating Scale (MADRS) scores at week 8. RESULTS: The MADRS scores improved by 15.9 points (95% CI 15.2-16.6) among patients who benefited from treatment. The proportion of patients who benefited from escitalopram and not from placebo treatment was 19.5%, corresponding to a number needed to treat of 5. CONCLUSIONS: This model gave a considerably better fit to the data than the analysis of covariance model in which all patients were assumed to benefit from treatment. The small average antidepressant-placebo difference obscures a much larger effect in a clinically meaningful subgroup of patients.
RCT Entities:
BACKGROUND: There is controversy about the implications of relatively small average drug-placebo differences observed in randomised controlled trials of antidepressant medications. AIMS: To investigate whether efficacy is better understood as a large effect in a subgroup of patients. METHOD: The mixture model was used to identify patient subgroups (patients benefiting or not benefiting from treatment) to directly model the skewness of Montgomery-Åsberg Depression Rating Scale (MADRS) scores at week 8. RESULTS: The MADRS scores improved by 15.9 points (95% CI 15.2-16.6) among patients who benefited from treatment. The proportion of patients who benefited from escitalopram and not from placebo treatment was 19.5%, corresponding to a number needed to treat of 5. CONCLUSIONS: This model gave a considerably better fit to the data than the analysis of covariance model in which all patients were assumed to benefit from treatment. The small average antidepressant-placebo difference obscures a much larger effect in a clinically meaningful subgroup of patients.
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