OBJECTIVE: Abacavir, a human immunodeficiency virus-1 (HIV-1) 
nucleoside-analogue reverse transcriptase inhibitor, causes severe 
hypersensitivity in 4-8% of patients. HLA B*5701 is a known genetic risk factor 
for abacavir hypersensitivity in Caucasians. Our aim was to confirm the presence 
of this genetic factor in our patients, and to determine whether genotyping for 
HLA B*5701 would be a cost-effective use of healthcare resources.
METHODS: Patients with and without abacavir hypersensitivity were identified 
from a UK HIV clinic. Patients were genotyped for HLA B*5701, and pooled data 
used for calculation of test characteristics. The cost-effectiveness analysis 
incorporated the cost of testing, cost of treating abacavir hypersensitivity, 
and the cost and selection of alternative antiretroviral regimens. A 
probabilistic decision analytic model (comparing testing versus no testing) was 
formulated and Monte Carlo simulations performed.
RESULTS: Of the abacavir hypersensitive patients, six (46%) were HLA B*5701 
positive, compared to five (10%) of the non-hypersensitive patients (odds ratio 
7.9 [95% confidence intervals 1.5-41.4], P = 0.006). Pooling of our data on HLA 
B*5701 with published data resulted in a pooled odds ratio of 29 (95% CI 
6.4-132.3; P < 0.0001). The cost-effectiveness model demonstrated that depending 
on the choice of comparator, routine testing for HLA B*5701 ranged from being a 
dominant strategy (less expensive and more beneficial than not testing) to an 
incremental cost-effectiveness ratio (versus no testing) of Euro 22,811 per 
hypersensitivity reaction avoided.
CONCLUSIONS: Abacavir hypersensitivity is associated with HLA B*5701, and 
pre-prescription pharmacogenetic testing for this appears to be a cost-effective 
use of healthcare resources.