Orexin A, Spinal Fluid
Test Mnemonic
ORXCSF
CPT Codes
- 83519 - QTY (1)
LOINC ®
91670-0
Aliases
- Hypocretin
- Hypocretin-1
Performing Laboratory
Mayo Clinic Dpt of Lab Med & Pathology
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1.5 mL | Cerebrospinal fluid (CSF) | Sterile container | Frozen | Obtain aliquot from second collection vial (preferred, not required). Specimens should be centrifuged to remove any red cells before shipping. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.5 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Frozen | 120 days |
| Ambient | Unacceptable |
| Refrigerated | Unacceptable |
Days Performed
Tue
Turnaround Time
4 - 29 days
Methodology
| Name | Description |
|---|---|
| Radioimmunoassay (RIA) |
Reference Range
Special Info
Hemolyzed specimens are unacceptable due to false-positive results.
Clinical Info
Aids in the diagnosis and differentiation of type 1 narcolepsy from other types of narcolepsy. This assay is not intended for use as a screening test. Narcolepsy affects 0.02% to 0.05% of the population and the onset of symptoms often occurs in adolescence. Orexin (also known as orexin-A or hypocretin-1) 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 (episodes of muscle weakness in response to emotional stimuli). An abnormally low concentration of orexin-A in cerebrospinal fluid (CSF) is indicative of what is termed type 1 narcolepsy. Survey of the literature reveals that approximately 85% to 95% of randomly selected individuals with type 1 narcolepsy and typical cataplexy, exhibit low (<110 pg/mL) CSF orexin concentrations.(1) In 1 large study, the sensitivity of this cutoff was found to be 87% with a specificity of 99%.(2) Orexin deficiency and type 1 narcolepsy are closely associated with HLA complex DQB1 *0602. It is estimated that only 1 in 500 HLA DQB1*0602-negative individuals exhibit low CSF orexin concentrations. CSF concentrations have been found to almost always be above 200 pg/mL in healthy individuals and those with nontype 1-narcoleptic sleep disorders such as narcolepsy type 2 and idiopathic hypersomnia.