Identifying clinically important difference on the Epworth Sleepiness Scale: results from a narcolepsy clinical trial of JZP-110

- Responder analyses can define clinically meaningful treatment effectiveness.
- There was concordance between patient and clinician ratings of improvement.
- For patients who respond to treatments, 25% reduction in ESS score is a clinically meaningful improvement threshold.

BackgroundWhile scores ≤10 on the Epworth Sleepiness Scale (ESS) are within the normal range, the reduction in elevated ESS score that is clinically meaningful in patients with narcolepsy has not been established.MethodsThis post hoc analysis of a clinical trial of patients with narcolepsy evaluated correlations between Patient Global Impression of Change (PGI-C) and ESS. Data of adult patients with narcolepsy from a double-blind, 12-week placebo-controlled study of JZP-110, a wake-promoting agent, were used in this analysis. Descriptive statistics and receiver operating characteristic (ROC) analysis compared PGI-C (anchor measure) to percent change from baseline in ESS to establish the responder criterion from patients taking either placebo or JZP-110 (treatments).ResultsAt week 12, patients (n = 10) who reported being “very much improved” on the PGI-C had a mean 76.7% reduction in ESS score, and patients (n = 33) who reported being “much improved” on the PGI-C had a mean 49.1% reduction in ESS score. ROC analysis showed that patients who improved were almost exclusively from JZP-110 treatment group, with an area-under-the-curve of 0.9, and revealed that a 25% reduction in ESS (sensitivity, 81.4%; specificity, 80.9%) may be an appropriate threshold for defining a meaningful patient response to JZP-110 and placebo.ConclusionsA ≥25% reduction in patients' subjective ESS score may be useful as a threshold to identify patients with narcolepsy who respond to JZP-110 treatment.