RESUMEN
To determine the prevalence of CYP2C9 polymorphism in normal Saudis [controls], in Saudi patients with venous thrombosis, in patients requiring low dose warfarin [study group] for anticoagulation, and to compare our results to those from other populations. Blood from the "control and study" groups was collected from November 2001 to November 2008. The DNA was extracted, stored at -70°C and later tested for the CYP2C9 polymorphism using established methods. Clinical data were collected through direct interview, chart review, and the Saudi Thrombosis and Familial Thrombophilia Registry. All individuals consented. The prevalence of CYP2C9 polymorphisms in the Saudi population was similar to Caucasians and higher than Asian and African. The control [n=670] and patients with venous thrombosis [n=110] groups showed similar prevalence of the normal wild type CYP2C9 and the 2 polymorphisms tested [CYP2C9*2 and CYP2C9*3]. The group that required low dose warfarin [n=25] showed significantly higher CYP2C9 polymorphism, required 40% less warfarin and had a higher rate of bleeding [5% versus 1.8%]. The prevalence of the abnormal polymorphism in the Saudi population of 35.5% is similar to that in Caucasians. Patients with the CYP2C9 polymorphism required 40% less warfarin and had more serious bleeds