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Epic Code LAB848 Narcolepsy-Associated Antigen, HLA-DQB1 Typing, Blood

Important Note

Order as Reference Miscellaneous #LAB848; indicate complete test name when ordering.

Additional Codes

Mayo Code: NARC

Reporting Name

Narcolepsy Associated Ag, B

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).

Useful For

Ruling out a diagnosis of narcolepsy

Performing Laboratory

Mayo Clinic Laboratories in Rochester


Specimen 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 Type

Whole Blood ACD-B

Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD-B Refrigerated (preferred)
  Ambient 

Day(s) Performed

Monday through Friday

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

An interpretive report will be provided.

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.

Cautions

No significant cautionary statements

Method 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 days

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

Clinical Reference

1. 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

2. Chabas D, Taheri S, Renier C, Mignot E: The genetics of narcolepsy. Ann Rev Genomics Hum Genet 2003;4:459-483

3. Andlauer O, Moore H 4th, Hong SC, et al: Predictors of hypocretin (orexin) deficiency in narcolepsy without cataplexy Sleep 2012 Sep 1;35(9):1247-1255F

4. Bassetti CLA, Adamantidis A, Burdakov D, et al: Narcolepsy - clinical spectrum, aetiopathophysiology, diagnosis and treatment. Nat Rev Neurol. 2019 Sep;15(9):519-539. doi: 10.1038/s41582-019-0226-9

5. 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 Dec;52:150-157. doi: 10.1016/j.sleep.2018.08.024

6. Miyagawa T, Tokunaga K: Genetics of narcolepsy. Hum Genome Var. 2019 Jan 8;6:4. doi: 10.1038/s41439-018-0033-7