Interpreting clinical trial results of patient-perceived onset of effect in asthma: methods and results of a Delphi panel

Objective: The purpose of this study was to determine if empirically observed differences in patient perception of, and satisfaction with, onset of effect between an active maintenance treatment and placebo are clinically meaningful to practicing clinicians. A secondary objective was to determine the lowest threshold for a clinically meaningful difference in terms of both between-group differences and maximum acceptable placebo effect. Methods: Twelve community-based healthcare professionals participated in a Delphi consensus panel. Panelists were provided with blinded results of two clinical trials showing statistically significant treatment effects for treatment A (budesonide/formoterol [Symbicort*]) over placebo in the proportion of patients who could perceive the medication working right away and the proportion of patients satisfied with this perception. Panelists were then asked to respond to a series of questions to identify a threshold for clinically important differences in patient-perceived onset of effect and satisfaction with speed of onset of effect. All expert panelists participated in two rounds of the Delphi process. Results: Panelists were unanimous in their conclusion that the statistically significant results from the two trials were clinically meaningful. According to these practitioners, the empirical results presented to them, showing that patients could feel a maintenance inhaler therapy work right away, were meaningful to clinical decision-making, and the attribute could potentially improve patient adherence with therapy. A group consensus was reached that a minimum active treatment response for these outcomes should range from 50% to 75% and be 2-3 times larger than the placebo response, with a maximum placebo effect of 26-40%. Conclusion: A Delphi panel study of practitioners was used to establish a meaningful range of response and a minimal important difference for interpreting results of clinical trials in which patient perception of onset of effect and satisfaction with this perception are tested. While the views of this panel may not be generalized to the entire population of practitioners in the United States, results provide insight into how a typical practitioner is likely to view clinical trial results and how the information might be used in clinical practice.