Scoring reliability of the multiple sleep latency test in a clinical population

STUDY OBJECTIVES: To determine intrarater and interrater scoring reliability of the multiple sleep latency test (MSLT) in a population of sleep clinic patients. DESIGN: N/A. SETTING: Urban sleep center. PATIENTS: 200 consecutive sleep center patients (diagnoses included: obstructive sleep apnea, narcolepsy, periodic-limb-movement, and individuals with no diagnosis). INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: MSLTs were recorded and scored according to standard clinical procedures. One of four clinical polysomnographers and one of seven polysomnographic technologists scored each MSLT. All MSLTs were then rescored by the same polysomnographer. The intrarater reliability coefficient for mean MSLT score was .87 and interrater reliability was .90. Coefficients for the mean number of REM onsets during the MSLT were .81 for intrarater and .88 for interrater reliability. Intrarater and interrater agreement (kappa coefficients) for the presence of at least one REM onset during the MSLT was .78 and .86, respectively. For the presence of greater than one REM onset, a kappa of .78 was obtained for intrarater agreement and .91 for interrater agreement. CONCLUSIONS: The clinical MSLT displays excellent interrater and intrarater reliability estimates for both sleep latency and REM onset scores in a sleep-disordered population.