Narcolepsy HLA-DQ Genotyping (HLA-DQB1*06:02)

Background Information for Narcolepsy (HLA-DQB1*06:02) Genotyping:
Characteristics: Narcolepsy is a chronic neurological sleep disorder that manifests in excessive daytime sleepiness and difficulty in maintaining wakefulness. Narcolepsy type 1 is associated with cataplexy (the sudden loss of muscle tone triggered by strong emotions). Additionally, disturbed nighttime sleep, sleep paralysis, and hypnagogic hallucinations (occurring in the period between sleep and wakefulness) are common.
Incidence: Varies, depending on ethnicity. It affects 0.02-0.05% of the populations in the U.S. and Europe; it is most common in Japan (0.16-0.18%).
Inheritance:  Multifactorial.
Cause: The HLA-DQB1*06:02 allele is strongly associated with narcolepsy, but by itself is not causative. Homozygosity for DQB1*06:02 allele doubles the risk, compared to heterozygous individuals.  
Alleles Tested: HLA-DQB1 alleles.
Clinical Sensitivity: 85-95 percent depending on ethnicity. Greater than 98% of affected Caucasians with cataplexy have the HLA-DQB1*06:02 allele.
Clinical Specificity: Less than 1 percent; 15-25 percent of unaffected Caucasians carry the HLA-DQB1*06:02 allele.
Methodology: Polymerase Chain Reaction/Massively Parallel Sequencing, or Polymerase Chain Reaction/Sequence-Specific Oligonucleotide Probe Hybridization
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Rare diagnostic errors may occur due to primer site mutations. Other genetic and nongenetic factors that influence narcolepsy disease are not evaluated. In cases where an HLA allele cannot be resolved unambiguously, the allele assignment will be reported as the most common, based on allele frequencies from the common, intermediate, and well-documented alleles catalog version 3.0.0 (Hurley CK, et al, 2020).

This test was developed and its performance characteristics determined by the Histocompatibility & Immunogenetics Laboratory at the University of Utah Health. It has not been cleared or approved by the U.S. Food and Drug Administration (FDA). The FDA has determined that such clearance or approval is not necessary. This test is used for clinical purposes. It should not be regarded as investigational or for research. The Histocompatibility & Immunogenetics Laboratory is certified under the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88) as qualified to perform high complexity clinical laboratory testing.

Performed at: Histocompatibility & Immunogenetics Laboratory, University of Utah Health, 417 Wakara Way, Suite 3220, Salt Lake City, UT 84108.

Counseling and informed consent are recommended for genetic testing. Consent forms are available online.