HLA-B*5701 Associated Variant Genotyping for Abacavir Sensitivity
Label Mnemonic: HLAB57
Epic Lab Code: LAB7880
Downtime Form: A-1a Miscellaneous Request
Commercial Mail-out Laboratory
5231 RCP
356-8593
Specimen(s):
Whole Blood
Collection Medium:
Lavender top tube 3 mL (EDTA)
Minimum:
Preferred Minimum: 3 mL whole blood in Lavender top tube.
Absolute Minimum: 1 mL whole blood in Lavender top tube.
Turn Around Time:
4-10 days upon receipt at reference laboratory.
Interpretive Data:
Characteristics: Abacavir sulfate is a nucleoside reverse transcriptase inhibitor (NRTI) used for the treatment of HIV. Abacavir hypersensitivity reaction is characterized by fever, rash, malaise, gastrointestinal, and respiratory symptoms. Symptoms typically appear within the first six weeks of treatment, worsen with each subsequent abacavir dose, and may be severe or fatal.

Incidence: HLA-B*5701 allele frequency varies by ethnicity: Indian 0.20, Thai 0.11, Caucasian 0.08, African American 0.02, Asian (rare).

Inheritance: Autosomal dominant.

Penetrance: 98 percent.

Cause: Abacavir hypersensitivity is strongly associated with the HLA-B*5701 allele. The mechanism is related to drug-specific activation of T lymphocyte killer cells.

Variant Tested: Single nucleotide polymorphism (SNP) rs2395029 in the HCP5 gene which is in linkage disequilibrium with HLA- B*5701.

Clinical Sensitivity and Specificity: 98 and 99 percent respectively, for immunologically confirmed hypersensitivity reaction.

Analytical Sensitivity and Specificity: 99 percent for prediction of HLA-B*5701 carrier status by SNP rs2395029 genotyping.
Comments:
Standard of care prior to abacavir therapy per FDA. Screening test to determine susceptibility to abacavir hypersensitivity syndrome.
Test Limitations:
Diagnostic errors can occur due to rare sequence variations. Rare recombination events between HCP5 SNP rs2395029 and HLA-B*5701 may occur. Alleles other than HLA-B*5701 will not be evaluated. Non-genetic factors that may affect drug sensitivity are not identified.
Methodology:
Polymerase Chain Reaction/Fluorescence Monitoring
CPT Code:
81381