Published: June 06, 2026, 00:26 UTC
Narcolepsy type 1 (NT1) is defined by the loss of orexin-producing neurons in the hypothalamus, leading to excessive daytime sleepiness, cataplexy, and fragmented nighttime sleep. A definitive diagnosis can be made by measuring orexin levels in cerebrospinal fluid, a test with high specificity. Yet in Australasia, this diagnostic tool remains underused.
A new case series from two Australian sleep centres, published in the Internal Medicine Journal, describes the use of CSF orexin testing in 15 clinically selected patients and highlights both its value and the barriers to its wider adoption.
The researchers, led by Mario Fernando at the Woolcock Institute of Medical Research in Sydney, analyzed patients referred for orexin testing due to clinical suspicion of NT1. The diagnosis of narcolepsy type 1 can be challenging because cataplexy, the hallmark symptom, is not always obvious or easy for patients to describe. Some patients present with atypical or subtle episodes of muscle weakness that may be mistaken for other conditions.
CSF orexin testing offers an objective biomarker. Levels below 110 pg/mL are considered diagnostic for NT1, with the test showing near-perfect specificity. In this cohort, the authors found that orexin testing confirmed NT1 in a subset of patients where clinical features alone were ambiguous, directly influencing treatment decisions.
Despite this utility, the test faces several hurdles in the Australasian setting. CSF collection requires a lumbar puncture, which is invasive and not always readily accepted by patients or referring physicians. Access to the assay itself is limited. Samples must be processed and stored according to strict protocols, and not all laboratories in Australia and New Zealand offer the test routinely.
The authors argue that greater awareness of orexin testing among sleep physicians and neurologists could reduce diagnostic delays. In many cases, patients with suspected NT1 are managed empirically without a definitive diagnosis, which may lead to suboptimal treatment choices or delays in accessing targeted therapies.
The study is small (15 patients) and descriptive, but it provides a practical, real-world snapshot of how orexin testing performs outside the highly controlled settings of clinical trials. For the sleep medicine community in Australasia, the message is that the test is underused relative to its diagnostic value.
Source: Fernando M, Cotta G, Kung S, et al. Cerebrospinal fluid orexin testing in Australians with narcolepsy type 1. Internal Medicine Journal, 2026. DOI: 10.1111/imj.70501