Background:The thrombin-generation assay has a variety of clinical uses, including diagnosis of thromboembolism-related disease, and particular profiles are associated with thrombophilic risk factors. The aim of this study was to evaluate the use of this assay in screening and identifying patients who require specific thrombophilic testing. Methods: We used a 2-step approach to perform specific thrombophilic testing and thrombin-generation assays on 169 consecutive patients. The first step was to identify particular profiles of thrombin generation corresponding to each type of thrombophilic risk factor and to determine the pertinent variables related to thrombin generation. We then performed ROC curve analysis for each predefined variable to determine the relevant cutoffs for identification of patients in need of further testing (negative predictive value, 100%). Results: Suggestive profiles were seen in factor V Leiden (n ‫؍‬ 49) and prothrombin (n ‫؍‬ 12) mutations and in protein S deficiency (n ‫؍‬ 12). ROC curves showed that factor V Leiden may be excluded when the difference between lag times obtained in the absence and presence of activated protein C (APC) is >1.5 min and that prothrombin G20210A may also be excluded when the peak thrombin concentration is <426 nmol/L. In addi-

Factor V G1691A (FV‐Leiden) and prothrombin (PRT) G20210A single nucleotide polymorphisms (SNPs) were associated with venous thrombosis among Caucasians. We assessed the contribution of both SNPs to the genetic susceptibility of deep venous thrombosis (DVT) among Lebanese and Tunisian patients. Subjects comprised 198 DVT patients and 540 healthy controls from Lebanon and 126 Tunisian DVT patients and 197 control subjects; FV‐Leiden (MnlI) and PRT G20210A (HindIII) genotyping was done by PCR‐RFLP. While the prevalence of FV‐Leiden mutant A allele and the G/A and A/A genotypes were significantly higher among DVT patients from Lebanon and Tunisia, the association of PRT G20210A with DVT was pronounced among Lebanese but not Tunisian patients. The prevalence of PRT G20210A mutant A allele (P < 0.001 vs. P = 181) and G/A genotype (P < 0.001 vs. P = 0.994) was significantly higher among Lebanese but not Tunisians, respectively. While FV‐Leiden was a common genetic risk factor for DVT in both communities, the contribution of PRT G20210A to the genetic susceptibility of DVT differed among Lebanese and Tunisians, which underscores the need to determine prothrombotic gene polymorphisms associated with DVT among Arab and Mediterranean basin communities. Am. J. Hematol. 81:641–643, 2006. © 2006 Wiley‐Liss, Inc.

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