Test-retest reliability of the multiple sleep latency test in narcolepsy without cataplexy and idiopathic hypersomnia.
OBJECTIVE
Differentiation of narcolepsy without cataplexy from idiopathic hypersomnia relies entirely upon the multiple sleep latency test (MSLT). However, the test-retest reliability for these central nervous system hypersomnias has never been determined.


METHODS
Patients with narcolepsy without cataplexy, idiopathic hypersomnia, and physiologic hypersomnia who underwent two diagnostic multiple sleep latency tests were identified retrospectively. Correlations between the mean sleep latencies on the two studies were evaluated, and we probed for demographic and clinical features associated with reproducibility versus change in diagnosis.


RESULTS
Thirty-six patients (58% women, mean age 34 years) were included. Inter -test interval was 4.2 ± 3.8 years (range 2.5 months to 16.9 years). Mean sleep latencies on the first and second tests were 5.5 (± 3.7 SD) and 7.3 (± 3.9) minutes, respectively, with no significant correlation (r = 0.17, p = 0.31). A change in diagnosis occurred in 53% of patients, and was accounted for by a difference in the mean sleep latency (N = 15, 42%) or the number of sleep onset REM periods (N = 11, 31%). The only feature predictive of a diagnosis change was a history of hypnagogic or hypnopompic hallucinations.


CONCLUSIONS
The multiple sleep latency test demonstrates poor test-retest reliability in a clinical population of patients with central nervous system hypersomnia evaluated in a tertiary referral center. Alternative diagnostic tools are needed.
Program in Sleep, Department of Neurology, Emory University School of Medicine, Atlanta, GA 30329, USA. Lbecke2@emory.edu
Lynn Marie
LM
Trotti
Beth A
BA
Staab
David B
DB
Rye
D000328:Adult; D002385:Cataplexy; D015331:Cohort Studies; D003937:Diagnosis, Differential; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D009290:Narcolepsy / Q000175:diagnosis*; D017286:Polysomnography; D015203:Reproducibility of Results
CNS hypersomnia; Multiple sleep latency test; idiopathic hypersomnia; narcolepsy without cataplexy; tes-tretest reliability