Test-Retest Reliability of Multiple Sleep Latency Test in Diagnosis of Narcolepsy

ABSTRACT

Objectives@#The diagnosis of hypersomnia may be changed by the repeated multiple sleep latency test (MSLT). We investigated the long-term reliability of MSLT in the diagnosis of narcolepsy type 1(NT1) and 2 (NT2). @*Methods@#We reviewed the data of patients with NT1 and NT2 who underwent MSLT at least twice between 2008 and 2020. The clinical information and polysomnography/MSLT data were thoroughly assessed, and two sleep experts evaluated the consistency and reliability of diagnosis independently. @*Results@#Eighty patients (38 with NT1 and 42 with NT2 as a final diagnosis) were included in this study. Of the 80 patients, 20 (nine with NT1 and 11 with NT2) underwent the 3rd MSLT. No significant differences were found in the sleep data and Epworth Sleepiness Scale at baseline. During the 2nd MSLT, 18.4% (n=7) patients with NT1 and 47.6% (n=20) patients with NT2 did not satisfy the diagnosis of narcolepsy. At the 3rd MSLT, six out of nine patients with NT1 and seven of 11 patients with NT2 were not suitable for narcolepsy. Two of the initial NT1 (5.2%) and 10 of the initial NT2 (23.8%) patients were found to be normal. Three patients who were confirmed to have NT1 through consecutive MSLTs had significantly shorter sleep latency and more number of sleep-onset rapid eye movements than the other patients. @*Conclusions@#The reliability of MSLT were not robust in the diagnosis of NT1 and NT2 in this long-term follow-up study. The MSLT results should be interpreted with careful consideration based on elaborate preparations.