HLA-B 1502 for carbamazepine toxicity

Genetic

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Pharmacogenetic markers.

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HLA-B*5702 for Carbamazepine Toxicity - Comprehensive Medical Test Guide

Why is it done?
- Test Purpose: HLA-B*5702 is a genetic test that identifies individuals who carry a specific human leukocyte antigen allele associated with severe, potentially life-threatening cutaneous adverse reactions to carbamazepine, an anticonvulsant and mood-stabilizing medication. This test measures the presence or absence of the HLA-B*5702 allele through DNA analysis.
- Primary Indications: Screening before initiating carbamazepine therapy; Evaluation in patients of Southeast Asian, Han Chinese, or other high-risk ancestry; Risk stratification for severe cutaneous adverse reactions including Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN); Assessment in patients with reported carbamazepine hypersensitivity
- Typical Timing: Performed prior to carbamazepine initiation (pre-emptive screening); Within the first weeks of therapy if screening was not done beforehand; At any time if adverse skin reactions develop during carbamazepine treatment. Most recommended as part of pharmacogenomic screening before medication initiation
Normal Range
- Reference Values: HLA-B*5702 Negative (Not Present): Absence of the HLA-B*5702 allele; HLA-B*5702 Positive (Present): Presence of one or two copies of the HLA-B*5702 allele
- Interpretation Categories: Negative Result: No HLA-B*5702 allele detected (homozygous negative); Heterozygous Positive: One copy of HLA-B*5702 allele present; Homozygous Positive: Two copies of HLA-B*5702 allele present (highest risk)
- Units of Measurement: Allele frequency or presence/absence (qualitative DNA testing); Results expressed as Present/Absent or as number of allele copies (0, 1, or 2)
- Normal vs. Abnormal: Normal (Negative Result): Indicates low genetic risk for carbamazepine-induced severe cutaneous adverse reactions; Abnormal (Positive Result): Indicates significantly increased risk for SJS/TEN with carbamazepine exposure; Carriers (heterozygous) have lower risk than homozygous carriers but still require caution
Interpretation
- Negative Result Interpretation: Patient does not carry the HLA-B*5702 allele; Low risk for carbamazepine-induced SJS/TEN based on genetic predisposition; Carbamazepine can generally be used with standard safety monitoring; Risk for SJS/TEN remains similar to general population baseline; Does not exclude other potential adverse reactions to carbamazepine
- Positive Result Interpretation: Patient carries at least one copy of the HLA-B*5702 allele; Significantly increased risk (up to 1000-fold increased risk) for carbamazepine-induced SJS/TEN; Alternative anticonvulsants or mood stabilizers should be considered; If carbamazepine use is absolutely necessary, requires careful patient education and close monitoring; Increased risk is most pronounced in first 8 weeks of therapy
- Factors Affecting Results: Ethnic ancestry (higher prevalence in Southeast Asian, Han Chinese, and other Asian populations); Age at testing does not affect genetic results; Previous carbamazepine exposure (genetic status unchanged); Presence of other HLA alleles or genetic factors; Concurrent medications that may interact with carbamazepine metabolism
- Clinical Significance of Result Patterns: Negative in high-risk population: Carbamazepine can be considered with standard monitoring; Positive in any population: Consider alternative medications first; Homozygous positive: Greatest clinical concern, alternative medications strongly recommended; Patient with history of SJS/TEN: Carbamazepine contraindicated regardless of HLA status; Family history of carbamazepine reaction with positive HLA-B*5702: Indicates strong genetic risk
Associated Organs
- Primary Organ Systems Involved: Integumentary system (skin): Primary target organ for carbamazepine-induced adverse reactions; Immune system: HLA-B*5702 allele presentation to T-cells triggers hypersensitivity cascade; Mucosal membranes: Involvement in SJS/TEN pathology; Liver: Secondary organ involvement in severe cutaneous reactions
- Associated Medical Conditions: Stevens-Johnson Syndrome (SJS): Severe mucocutaneous reaction with skin detachment <10%; Toxic Epidermal Necrolysis (TEN): Life-threatening condition with >30% skin detachment; SJS/TEN overlap syndrome: Involvement of 10-30% of body surface; Carbamazepine hypersensitivity syndrome: Systemic manifestations with fever, rash, and lymphadenopathy; Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome
- Potential Complications and Risks: Mortality: SJS/TEN mortality rates of 1-5% (SJS) and 25-35% (TEN); Severe dehydration and electrolyte imbalances; Secondary bacterial infections; Respiratory tract involvement requiring intubation; Ocular complications including blindness; Gastrointestinal perforation; Acute kidney injury; Sepsis and multiorgan failure; Long-term scarring and functional impairment; Psychological trauma and quality of life impact
- Diseases Aided by This Test: Epilepsy (treatment planning); Trigeminal neuralgia (medication selection); Bipolar disorder (mood stabilizer option assessment); Mixed anxiety-depressive disorder (alternative to carbamazepine needed); Neuropathic pain syndromes (medication safety evaluation); Alcohol withdrawal seizures (prevention strategy determination)
Follow-up Tests
- Additional Tests Based on Positive Results: HLA-A*3101 testing: Additional genetic risk marker for carbamazepine-induced adverse reactions; Comprehensive metabolic panel: If carbamazepine must be used despite positive HLA-B*5702; Complete blood count: Baseline and monitoring during carbamazepine therapy; Liver function tests: To monitor for hepatotoxicity; Extended HLA typing: Assessment for other relevant HLA alleles
- Further Investigations If Carbamazepine Used: Skin examination at each visit (first 12 weeks critical); Drug allergy patch testing if reaction develops; Lymphocyte stimulation test (LST) for carbamazepine sensitivity; Histopathological examination if rash develops; Ophthalmologic examination if eye involvement suspected
- Monitoring Frequency for Ongoing Conditions: If negative result and carbamazepine initiated: Clinical assessment at 2 weeks, then at monthly intervals; If positive result but carbamazepine absolutely necessary: Weekly clinical evaluation for first 4 weeks, then bi-weekly for next 8 weeks, then monthly; Laboratory monitoring: LFTs at baseline, 2 weeks, 1 month, then every 3 months; Carbamazepine serum levels: At steady state (after 3-5 days) and with dose adjustments
- Related Complementary Tests: Carbamazepine serum level testing: Therapeutic drug monitoring; CYP3A4 genotyping: Affects carbamazepine metabolism; Comprehensive pharmacogenomic panel: Assessment for other drug sensitivities; Immunologic testing: If hypersensitivity syndrome develops; Viral serology: For HHV-6 reactivation association with carbamazepine reactions
Fasting Required?
- Fasting Status: No fasting required
- Specimen Collection Requirements: Blood sample via venipuncture (typically 5-10 mL); Sample collected in EDTA tube (lavender-top) for DNA extraction; Saliva sample may be alternative in some laboratories; Buccal swab collection possible for some testing methods
- Patient Preparation Instructions: No special dietary restrictions; Adequate hydration is acceptable; Normal medications may be continued; Patient should inform provider of any recent blood transfusions or bone marrow transplants; No fasting period needed (can eat and drink normally before test)
- Medications - No Restrictions: All current medications should be continued as prescribed; Genetic testing is not affected by medication use; No need to hold carbamazepine or any other medications before testing; Continue all routine medications and supplements normally
- Other Preparation Details: Timing of collection: Can be performed any time of day; No special clothing or positioning required; Standard blood draw precautions apply; Result turnaround time: Typically 1-2 weeks for HLA genotyping; Patient should have informed consent discussion regarding pharmacogenomic implications

How our test process works!