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

BACKGROUND

While 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.

METHODS

This 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).

RESULTS

At 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.

CONCLUSIONS

A ≥25% reduction in patients' subjective ESS score may be useful as a threshold to identify patients with narcolepsy who respond to JZP-110 treatment.