This is actually not relevant as warfarin dosage is determined by regular testing and dose adjustment. Your inborn metabolic rate is a very small effect compared to, for example, dietary preferences. (for those who are unfamiliar with the agent, warfarin antagonises the effects of vitamin K and so must be adjusted against dietary intake)

Unfortunately there are many people in the health sector offering tests that, whilst factually correct, are irrelevant to a patient's care.