ABSTRACT:
Introduction: Over the last Century, Thousands of studies were conducted to highlight the factors affecting warfarin efficacy and toxicity. Many of these studies had major limitations because they focused only on one or a few factors. Objectives: to determine the effect of 14 different clinical and genetic factors on the clinical outcomes (efficacy and toxicity) of warfarin in Egyptian patients with autoimmune diseases. The secondary objective was detecting the association between genetic polymorphisms of VKORC1 (rs 9923231) and systemic lupus erythematosus (SLE) susceptibility in the Egyptian population. Methods: after signing a consent form, 150 patients were included in the study from Kasr Aleiny Hospital, Cairo University. All medical records were reviewed to extract the effect of age, sex, diagnoses, genotypes, warfarin-drug interactions, and all patients' comorbidities on warfarin's efficacy and toxicity. The average warfarin doses, INR, (No. of times)/total times of INR within the therapeutic range, differences between the maximum and minimum INR values, the addition of enoxaparin and discontinuing warfarin and shifting to Rivaroxaban, and bleeding episodes were determined. Results: all the studied factors had clinical and statistical significance on the clinical outcomes. The T allele was associated with treatment failure and a shift to rivaroxaban, a higher risk of bleeding and SLE. Conclusions: Awareness of the effect of the factors addressed in this study is mandatory for the assessment of warfarin efficacy and toxicity for each patient. Further studies are essential in other specialties because different warfarin-drug interactions may be detected, with other comorbidities and on different genes.