An RCT of genotype-guided versus conventional therapy showed that HLA-B*5701 genotyping could eliminate serious skin reactions during initiation of abacavir.65 On the other hand, RCTs of genotype-guided versus conventional warfarin therapy have shown either no difference34 or a small difference35 in time in therapeutic range (TTR) during the first 30–90 days of treatment. Whether the TTR is the appropriate metric for such a trial, the role of ancestry might play in determining these results, and the question of genetics and long-term bleeding risk discussed above are still open issues.
