Determination of thresholds for minimally important difference and clinically important response on the functional outcomes of sleep questionnaire short version in adults with narcolepsy or obstructive sleep apnea

PURPOSE: This study estimated thresholds for clinically important responses and minimally important differences for two indicators of improvement for the 10-item version of the functional outcomes of sleep questionnaire (FOSQ-10). METHODS: Participants with excessive daytime sleepiness with narcolepsy or obstructive sleep apnea received 12 weeks of solriamfetol treatment. Participants completed the FOSQ-10 and other patient-reported outcome measures, including the single-item patient global impression of change (PGI-C) assessment. Clinicians completed the single-item clinician global impression of change (CGI-C) for each participant. Data from the two studies were analyzed separately, both without regard to treatment assignment. In total, 690 participants (47% female, mean age 48 years, 77% Caucasian, 91% from North America) were enrolled. Two clinically important changes, defined as a minimally important difference and a clinically important response, were determined using distribution and anchor-based analyses. A receiver operating characteristic analysis was used to determine the optimal FOSQ-10 change threshold. RESULTS: Spearman correlations between change in FOSQ-10 scores and PGI-C and CGI-C were − 0.57 and − 0.49 for participants with narcolepsy and − 0.42 and − 0.37 for participants with obstructive sleep apnea. Receiver operating characteristic analysis suggested minimally important difference and clinically important response estimates of 1.7 and 2.5 and 1.8 and 2.2 points in narcolepsy and obstructive sleep apnea, respectively. CONCLUSIONS: Minimally important difference and clinically important response estimates for the FOSQ-10 for adults with excessive daytime sleepiness in narcolepsy or obstructive sleep apnea will be helpful for interpreting changes over time and defining a clinical responder. CLINICALTRIALS.GOV IDENTIFIERS: NCT02348593 (first submitted January 15, 2015) and NCT02348606 (first submitted January 15, 2015)