OBJECTIVE: To evaluate the clinical impact and cost-effectiveness of HLA-B*5701 
testing to guide selection of first-line HIV regimens in the United States.
DESIGN: Cost-effectiveness analysis using a simulation model of HIV disease. The 
prevalence of HLA-B*5701 and the probabilities of confirmed and unconfirmed 
severe systemic hypersensitivity reaction among patients taking abacavir testing 
HLA-B*5701 positive and negative were from the Prospective Randomized Evaluation 
of DNA Screening in a Clinical Trial study. The monthly costs of abacavir-based 
and tenofovir-based regimens were $1135 and $1139, respectively; similar 
virologic efficacy was assumed and this assumption was varied in sensitivity 
analysis.
PATIENTS: Simulated cohort of patients initiating HIV therapy.
INTERVENTIONS: The interventions are first-line abacavir, lamivudine, and 
efavirenz without pretreatment HLA-B*5701 testing; the same regimen with 
HLA-B*5701 testing; and first-line tenofovir, emtricitabine, and efavirenz.
MAIN OUTCOME MEASURES: Quality-adjusted life years and lifetime medical costs 
discounted at 3% per annum, cost-effectiveness ratios ($/QALY).
RESULTS: Abacavir-based treatment without HLA-B*5701 testing resulted in a 
projected 30.93 years life expectancy, 16.23 discounted quality-adjusted life 
years, and $472,200 discounted lifetime cost per person. HLA-B*5701 testing 
added 0.04 quality-adjusted months at an incremental cost of $110, resulting in 
a cost-effectiveness ratio of $36,700/QALY compared with no testing. Initiating 
treatment with a tenofovir-based regimen increased costs without improving 
quality-adjusted life expectancy. HLA-B*5701 testing remained the preferred 
strategy only if abacavir-based treatment had equal efficacy and cost less per 
month than tenofovir-based treatment. Results were also sensitive to the cost of 
HLA-B*5701 testing and the prevalence of HLA-B*5701.
CONCLUSION: Pharmacogenetic testing for HLA-B*5701 is cost-effective only if 
abacavir-based treatment is as effective and costs less than tenofovir-based 
treatment.