Wednesday, February 14, 2024

HLA-DQB1-Susceptibility to narcolepsy, genotype, total blood

Description, Result Format, Alleles Studied and Reference values Modification

Test code: 4027
Mnemonic codeHLDQ

Effective update from 26/02/2024


Description:HLA-DQB1-Susceptibility to narcolepsy, genotype, total blood

Result format:
R1: Result

Alleles studied: DQA1*0102, DQB1*0602 

Reference values:         
      *Alleles DQA1*0102, DQB1*0602
Version of Test: 3

Result format:
R1: Sample
R2: Result        
Alleles studied: DQB1*0602      
Reference values:

Interpretation and recommendations
Narcolepsy is a rare neurological disease (0.02-0.05% of world's population) characterized by severe drowsiness, uncontrollable sleep attacks, sleep paralysis, and hallucinations.
Type 1 narcolepsy presents cataplexy and decreased levels of hypocretin-1 in cerebrospinal fluid due to deterioration of orexin/hypocretin neurons; Type 2 presents with normal hypocretin levels and without cataplexy.
Eventhough its cause is not completely clear, genetic factors are relevant since more than 98% of type 1 narcoleptic patients are carriers of HLA-DQB1*06:02 allele, frequently in combination with HLA DRB1*15:01. Despite its strong association, around 20% of general population are also carriers of this allele, so, although HLA-DQB1*06:02 allele is not included in the diagnostic criteria for narcolepsy, it is useful due to its high negative predictive value (98-99%).
This report should be evaluated by a specialist within the clinical context and family history of the patient, in conjunction with other laboratory findings. Genetic counseling is recommended.

Test Method
DNA extraction followed by real-time PCR amplification (CE-IVD commercial method) of  HLA-DQB1*06:02 allele group, associated with narcolepsy susceptibility, and of an HBB gene fragment (β-globin) as internal positive control.
Version of Test: 4
Test limitations
Variants other than those studied are not analyzed.
Normal/polymorphic genomic variation in the patient may interfere with variant detection in the sample.

Mignot, E. et al. (1997). Sleep, 20(11):1012-1020
Cano, P. et al. (2007). Human Immunology, 68:392–417
Tafti, M. et al. (2014). Sleep, 37(1):19-25 
Miyagawa, T. et al. (2019). Human genome variation 6:4

Version of Test: 4

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