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Test Code NARC Narcolepsy-Associated Antigen, HLA-DQB1 Typing, Blood

Reporting Name

Narcolepsy Associated Ag, B

Useful For

Ruling out a diagnosis of narcolepsy

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood ACD-B


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 Minimum Volume

3 mL

Specimen Stability Information

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

Reference Values

An interpretive report will be provided.

Day(s) Performed

Monday through Friday

Test 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.

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

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).

Report Available

3 to 8 days

Reject Due To

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

Method Name

Polymerase Chain Reaction (PCR)/Sequence-Specific Oligonucleotide Probes (SSO)