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

Additional Codes

 

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
NARCOLEPSY-ASSOCIATED ANTIGEN, HLA-DQB1 TYPING LABNARC NARC NARC

 

Reporting Name

Narcolepsy Associated Ag, B

Useful For

Ruling out a diagnosis of narcolepsy

Method Name

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

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type

Whole Blood ACD-B


Specimen Required


Container/Tube: Yellow top (ACD solution B)

Specimen Volume: 6 mL

Collection Instructions: Do not transfer blood to other containers.

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
Whole Blood ACD-B Refrigerated (preferred)
  Ambient 

Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

 

Reference Values

An interpretive report will be provided.

Day(s) and Time(s) Performed

Monday through Friday; 7:30 a.m.-5:00 p.m.

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 In Process

 

Result ID Test Result Name Result LOINC Value
NARC_ Narcolepsy Associated Ag Result 53938-7
NARCC Interpretation No LOINC Needed

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 Description

This assay applies Luminex technology to the reverse sequence specific oligonucleotide DNA typing method. First, target DNA is 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 HLA typing is based on the reaction pattern compared to patterns associated with published HLA gene sequences.(Package insert: One Lambda, LABType SSO Typing Tests, rev 18, 2010)

Analytic Time

5 days

Clinical Information

Narcolepsy is a neurological condition affecting about 0.02% of African American, Caucasian, 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, Caucasian, 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).

Test Classification

This test has been cleared or approved by the U.S. 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.