<International Circulation>: Is this been done routinely anywhere in the world at the moment， including the USA?

    Prof. Lee: Not yet. In the US at least， these private companies and insurers are becoming more aware. The major hurdle remains – how do we do the molecular diagnostics? Currently， private diagnostic labs can provide mucous swab results but it takes time and it is still not routinely performed in local hospitals.

    <International Circulation>: What’s the difference between the warfarin dose derived using a pharmacogenetic algorithm and the classical dose. What are the reasons for any differences?

    Prof. Lee: The best example I can give is in terms of race. We know that Africans require higher doses than Caucasians and Asians， and that Caucasians require higher warfarin doses than Asians. Based on the classical way of prescribing warfarin and considering race， then if the patient is Asian then one starts lower. The problem is there are sensitive patients amongst the African and Caucasian population. Sensitive meaning they require lower warfarin doses. And there are resistant patients in the Asian population. If you prescribe on race alone， you will still make mistakes but when incorporating pharmacogenomics， race is very relevant， because differences in race are explained by genetics. So we can fine-tune our dosage. The beauty of pharmacogenetic algorithms is also that they add height， age and weight so as to achieve a more accurate estimate of the dose required. Another commonly used example is the fact that warfarin has drug-drug interactions. For instance， when people are taking amiodarone in conjunction with warfarin， they should lower the warfarin dose – which sounds simple if there were just two groups， those on amiodarone and those without amiodarone. For the most sensitive group with the CYP2C9 and the VKORC1 mutations (which are the sensitive genotypes)， even if you give lower doses， this most extreme sensitive group is still at risk of overdosing. With genomics we are able to more precisely fine-tune what a patient’s most likely dose is to be which is， of course， a benefit. The other benefit of pharmacogenomic testing is that it gives the physician an idea that their patient belongs to a certain group， whether it be resistant (requiring higher doses)， intermediate (the average) or sensitive (in whom reducing dosage will prevent hemorrhage).