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HelpEpic Code LAB848 Narcolepsy-Associated Antigen, HLA-DQB1 Typing, Blood
Additional Codes
Mayo Code: NARC
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Ruling out a diagnosis of narcolepsy
Specimen Type
Whole Blood ACD-BSpecimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A), lavender top (EDTA)
Specimen Volume: 6 mL
Collection Instructions: Send whole blood specimen in original vial. Do not aliquot.
Additional Information: Specimen acceptability is based on extracted DNA concentration and not sample age.
Specimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood ACD-B | Refrigerated (preferred) | ||
| Ambient | |||
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Day(s) Performed
Monday through Friday
Reference Values
An interpretive report will be provided.
Clinical Information
Narcolepsy is a neurological condition affecting about 0.02% of African American, White, and Japanese individuals. It is characterized by excessive daytime somnolence and abnormal rapid eye movement (REM) sleep. Cataplexy (weakness precipitated by emotions, especially laughter) is present in 64% to 79% of patients with narcolepsy.
Studies have identified DQB1*06:02 as a useful marker of narcolepsy. DQB1*06:02 is found in 90% to 95% of African American, White, and Japanese patients with narcolepsy who also have cataplexy (narcolepsy type 1), but only in 45% to 50% of patients with narcolepsy without cataplexy (narcolepsy type 2). It must also be clearly understood that about 25% of normal people have this gene.
Because DQB1*06:02 is present in the normal population, no test for an HLA gene constitutes a test for narcolepsy. A more reliable approach would be to consider that, in an appropriate patient who has cataplexy, the absence of the strongly associated DQB1*06:02 provides good evidence that the patient does not have narcolepsy. However, its absence does not rule-out narcolepsy without cataplexy (narcolepsy type 2).
Cautions
Based on the catalog of common, intermediate, and well-documented alleles in the world population,(1) certain intermediate or common alleles in some ethnicities may not be resolved.
Interpretation
If DQB1*06:02 is not detected, the narcolepsy-associated antigen test result will be reported as negative for DQB1*06:02.
If the allele is detected, the result will be reported as positive for DQB1*06:02.
Reporting Name
Narcolepsy Associated Ag, BMethod Name
Polymerase Chain Reaction (PCR)/Sequence-Specific Oligonucleotide Probes (SSO)
Method Description
This assay applies Luminex technology to the reverse sequence specific oligonucleotide DNA typing method. First, target DNA is polymerase chain reaction (PCR)-amplified using a group-specific primer. The PCR product is biotinylated, which allows it to be detected using r-phycoerythrin-conjugated streptavidin. The PCR product is denatured and allowed to rehybridize to complementary DNA probes conjugated to fluorescently coded microspheres. A flow analyzer identifies the fluorescent intensity of phycoerythrin on each microsphere. The HLA class II allele or allele groups of the sample are determined by the positive and negative bead identified using a computer software program. The assignment of the human leukocyte antigen (HLA) typing is based on the reaction pattern compared to patterns associated with published HLA gene sequences.(Package insert: LABType SSO Typing Tests. One Lambda; Version 04, 11/11/2019)
CPT Code Information
81376-HLA Class II typing, low resolution (eg, antigen equivalents); one locus (eg, HLA-DRB1/3/4/5, -DQB1, -DQA1, -DPB1, or -DPA1), each
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| NARC | Narcolepsy Associated Ag, B | 63558-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| NARC_ | Narcolepsy Associated Ag Result | 63558-1 |
| NARCC | Interpretation | 50595-8 |
Report Available
3 to 8 daysTest Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.Clinical Reference
1. Hurley CK, Kempenich J, Wadsworth K, et al. Common, intermediate and well-documented HLA alleles in world populations: CIWD version 3.0.0. HLA. 2020;95(6):516-531. doi:10.1111/tan.13811
2. Mignot E, Lin X, Arrigoni J, et al. DQB1*0602 and DQB1*0102 (DQ1) are better markers than DR2 for narcolepsy in Caucasian and Black Americans. Sleep 1994;17:S60-67
3. Chabas D, Taheri S, Renier C, Mignot E. The genetics of narcolepsy. Ann Rev Genomics Hum Genet 2003;4:459-483
4. Andlauer O, Moore H 4th, Hong SC, et al. Predictors of hypocretin (orexin) deficiency in narcolepsy without cataplexy Sleep 2012;35(9):1247-1255F
5. Bassetti CLA, Adamantidis A, Burdakov D, et al. Narcolepsy - clinical spectrum, aetiopathophysiology, diagnosis and treatment. Nat Rev Neurol. 2019;15(9):519-539. doi:10.1038/s41582-019-0226-9
6. Capittini C, De Silvestri A, Terzaghi M, et al. Correlation between HLA-DQB1*06:02 and narcolepsy with and without cataplexy: approving a safe and sensitive genetic test in four major ethnic groups. A systematic meta-analysis. Sleep Med. 2018;52:150-157
7. Miyagawa T, Tokunaga K: Genetics of narcolepsy. Hum Genome Var. 2019;6:4. doi:10.1038/s41439-018-0033-7