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HelpTest Code NARC Narcolepsy-Associated Antigen, HLA-DQB1 Typing, Blood
Reporting Name
Narcolepsy Associated Ag, BUseful For
Ruling out a diagnosis of narcolepsy
Method Name
Polymerase Chain Reaction (PCR)/Sequence-Specific Oligonucleotide Probes (SSO)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
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.Reference Values
An interpretive report will be provided.
Day(s) Performed
Monday through Friday
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 |
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).
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
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.
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)