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Testing to diagnose type 1 narcolepsy
Orexin is a neuropeptide produced in the hypothalamus and is involved in the sleep/wake cycle in humans. Impairment of orexin production and orexin-modulated neurotransmission is associated with narcolepsy with cataplexy. An abnormally low concentration of orexin-A/hypocretin-1 in cerebrospinal fluid (CSF) is indicative of type 1 narcolepsy. The low CSF orexin-A/hypocretin-1 assay has over 90% sensitivity and specificity for the diagnosis of type 1 narcolepsy.
The multiple sleep latency test (MSLT) is the typical method for the diagnosis and differentiation of narcolepsy, but several factors can interfere with this method and produce inconclusive results. Alternatively, determining orexin-A/hypocretin-1 levels through CSF testing provides a sensitive and specific result to guide appropriate treatment for patients.
A Test in Focus
Michael Silber, M.B., Ch.B., a neurologist in the sleep medicine department at Mayo Clinic, provides a clinical perspective of narcolepsy, discussing limitations of current testing methods and the advantages of ordering the orexin-A/hypocretin-1 test.
Learn more about how to order this evaluation at your institution.
When should I order this test?
This test can be used for any patient with symptoms of narcolepsy with cataplexy. It is specifically recommended for patients suspected of having narcolepsy in which an MSLT is difficult to interpret due to:
- Shift work
- Insufficient sleep
- Confounding medications
- Presence of untreated or partially treated sleep apnea
- A young age in which the MSLT test is not valid by itself
Which test should I order?