A client with ancestry from a population in which HLA-B*1502 is found is prescribed carbamazepine for the first time. Which test should the nurse verify before therapy begins?
1HLA-B*1502 genetic screening✓ Correct answer
2A serum digoxin concentration
3An international normalized ratio
4A high-sensitivity cardiac troponin level
Explanation
Carbamazepine labeling recommends HLA-B*1502 screening before treatment in clients with ancestry from genetically at-risk populations because the allele is strongly associated with Stevens-Johnson syndrome and toxic epidermal necrolysis. A negative result does not replace ongoing assessment for rash or mucosal symptoms. Digoxin concentration, INR, and troponin do not screen for this carbamazepine-specific genetic risk.
Clinical reasoning HLA-B*1502 is associated with carbamazepine-induced SJS/TEN in genetically at-risk populations. Verify screening before the first dose when ancestry indicates risk.
Decision rule Genetic screening reduces risk but does not eliminate the need to stop and urgently evaluate a new blistering rash or mucosal lesion.
Scenario 42-year-old female of Han Chinese descent with trigeminal neuralgia; provider prescribes carbamazepine 200 mg PO BID. No prior anticonvulsant exposure.
HLA-B*1502 — An HLA allele associated with a markedly increased risk of carbamazepine-related SJS/TEN in certain genetically at-risk populations.
Stevens-Johnson syndrome and toxic epidermal necrolysis — Severe, potentially fatal mucocutaneous reactions that require immediate drug evaluation and emergency care.
Pharmacogenomic screening — Genetic testing used to predict serious drug reactions and tailor therapy; standard for HLA-B*1502 with carbamazepine in at-risk ancestries.