Correlation between the Epworth Sleepiness Scale and the Maintenance of Wakefulness Test in Obstructive Sleep Apnea Patients Treated with Positive Airway Pressure

Background. - The Epworth sleepiness scale (ESS) is often used to evaluate the impact of treatment in patients with obstructive sleep apnea hypopnea syndrome (OSA). We aimed to evaluate the correlation between ESS and the Maintenance of Wakefulness Test (MWT) in a population of OSA patients treated with positive airway pressure (PAP). Methods. - We retrospectively included all patients during a 2-year period who were diagnosed with OSA in our sleep clinic and required PAP therapy. ESS was evaluated at baseline and after PAP therapy for all patients, and all had a concomitant MWT. Correlation between final ESS, change in ESS, and MWT were evaluated using Spearman's correlation. Given that MWT is considered as the gold standard, the diagnostic performance of ESS was evaluated against MWT. Results. - Hundred thirty-four OSA patients were included. At the time of MWT, 89.6% of the patients were compliant (PAP use >= 4 hours/night), and only 9 (6.7%) had persistent sleepiness despite PAP treatment (mean sleep latency at MWT < 19.4 min). Moderate correlation was observed between final ESS and MWT (Spearman's correlation coefficient = -0.42), but no correlation was found between change in ESS and MWT. Diagnostic performance was as follows for final ESS: sensitivity = 55.6%, specificity = 84.8%, PPV = 20.8%, and NPV = 96.4%. Conclusions. - ESS was moderately correlated with MWT in a population of OSA patients compliant with PAP therapy. In this population, ESS showed poor diagnostic performance in identifying patients with persistent excessive daytime sleepiness.