Despite the substantial number of work published over the past years in different populations around the world, a fundamental gap remains in understanding whether and how genomic admixture and polymorphisms in warfarin-related pharmacogenes account for the high inter-individual dose variability observed in Caribbean Hispanic patients. In addition to being a medically underserved population, often marginally represented in clinical studies, Caribbean Hispanics are also a genomically heterogeneous population whose high level of admixture has produced a rich repertoire of combinatorial genotypes (e.g., CYP2C9*2/*5 + VKORC1-1639 A/A) that appear to challenge current pharmacogenetic-driven prescribing models. Our project takes a novel approach to definitively assess this admixture component and is also highly practical for its incorporation into a customized pharmacogenetic algorithm that will be implemented in "real-world" clinical settings through a web-based portal. Moreover, the project is also aimed at performing DNA-sequencing to identify those unknown variants on candidate pharmacogenes (i.e., CYP2C9 and VKORC1) that may contribute further to explain dose variability in Caribbean Hispanics. Shaped by strong preliminary data from a SC2 pilot project, the investigators will assess clinical validity and utility of an admixture-adjusted, pharmacogenetic-guided prescribing model for personalized prediction of effective warfarin dosing in Caribbean Hispanics, which also encompasses genetic (common and novel variants) and non-genetic clinical and demographic factors. The study will be conducted over 4 years in 300 patients with thromboembolic disorders receiving warfarin. Four collaborating/recruiting sites will be further connected through precise delivery of genotyping results and prescribing advice to clinicians via a web-based portal. Our novel assessment of genetic admixture will quantify the contribution of European, African and Amerindian ancestry, and the investigators will test whether this admixture component can explain the heritability that is currently missing in the response variability to this drug among Caribbean Hispanics. If successful in our target population, the same approach can ultimately render current pharmacogenomic models for clinical management of related thromboembolic conditions more accurate and predictive for other populations.