WHAT IS KNOWN AND OBJECTIVE: Warfarin is an oral anticoagulant which has been 
widely used to treat and prevent thromboembolic events. Managing warfarin 
therapy requires careful monitoring and dose titration. This randomized 
controlled study was designed to assess the effect of genotype-guided warfarin 
anticoagulation in Chinese elderly patients with nonvalvular atrial 
fibrillation.
METHODS: 507 adults were randomized to receive initial dosing as determined by 
an algorithm containing genetic (VKORC1 and CYP2C9) plus clinical information or 
only clinical information. The primary endpoint was the time in therapeutic 
range (TTR) over 90 days. Secondary end points included haemorrhagic events, 
thrombotic events and mortality.
RESULTS: The TTR was significantly different between genetic group and control 
group. The average TTR was (70.80 ± 24.39) % in the genotype-guided group as 
compared with (53.44 ± 26.73) % in the control group. This represents a 
difference of 17.36% (95% CI, 11.82 to 22.89, P < .001). The cumulative 
incidence of total haemorrhagic events, minor haemorrhagic events, 
gastrointestinal bleeding and intracerebral bleeding events was not 
significantly different between two groups (P > .05). Follow-up showed that the 
cumulative incidence of ischaemic stroke events occurred in the genetic group 
was significantly lower than that in the control group (2.39% vs 6.82%), and the 
genetic group had a significant lower risk than control group in cumulative 
incidence of ischaemic stroke events [HR 0.22, (95% CI 0.065 to 0.77), P < .05].
WHAT IS NEW AND CONCLUSION: Genotype-guided dosing could improve the average 
TTR, and follow-up result showed that genotype-guided therapy resulted in a 
significantly lower risk of ischaemic stroke events. Further research is 
required to focus on the clinical benefit of genotype-guided dosing.