Orexin-A/Hypocretin-1, Spinal Fluid
Use
This test is useful for aiding in the diagnosis and differentiation of type 1 narcolepsy from other causes of hypersomnolence. Orexin-A (hypocretin-1) is a neuropeptide involved in the sleep/wake cycle in humans. An abnormally low concentration of orexin-A (hypocretin-1) in cerebrospinal fluid (CSF) indicates type I narcolepsy. Cerebrospinal fluid concentrations have been found to almost always be above 200 pg/mL in healthy individuals and those with non-type 1-narcoleptic sleep disorders, such as narcolepsy type 2 and idiopathic hypersomnia.
Special Instructions
Patient should not have recently received radioisotopes, either therapeutically or diagnostically, due to potential assay interference. Specimens will be screened for radioactivity prior to analysis. Complete and send a Neurology Specialty Testing Client Test Request (T732) with the specimen if not ordering electronically.
Limitations
The assay is not intended for use as a screening test. Orexin deficiency in HLA (human leukocyte antigen) DQB1*0602-negative patients is rare. This test may be considered for the diagnosis of narcolepsy type 1 after HLA positivity is shown if a clinical multiple sleep latency test is negative or unavailable due to potential confounding circumstances. Orexin concentrations between 111 pg/mL and 200 pg/mL are considered intermediate and have limited diagnostic utility for type 1 narcolepsy as they may be representative of other neurological disorders. The test should not be requested in patients who have recently received radioisotopes as potential assay interference may occur.
New York Approved
Methodology
Immunoassay (RIA)
Biomarkers
LOINC Codes
- 91670-0
- 91670-0
Result Turnaround Time
3-32 days
Related Documents
For more information, please review the documents below
Specimen
Cerebrospinal Fluid
Volume
1.5 mL
Minimum Volume
0.5 mL
Container
Sterile vial
Collection Instructions
Obtain aliquot from second collection vial (preferred, not required). Hemolyzed specimens will give false-positive results. Specimens should be centrifuged to remove any red cells prior to shipping.
Patient Preparation
Patient should not have recently received radioisotopes, either therapeutically or diagnostically, due to potential assay interference.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 72 hours |
| Refrigerated | 7 days |
| Frozen | 120 days |