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Background: Previous analyses reported a higher risk of recurrent venous thrombosis in men than women., Objectives: We aimed to assess the risk of recurrence in men compared with women whilst taking female reproductive risk factors (oral contraception, postmenopausal hormone therapy and pregnancy) into account. In addition, we hypothesized that the sex difference in venous thrombosis was related to F9 Malmö, an X-linked prothrombotic factor., Methods: In four pooled European cohorts (CARROT study, Glasgow, UK; CVTE study, Cambridge, UK; AUREC study, Vienna, Austria; and LETS follow-up study, Leiden, the Netherlands), the risk of recurrent venous thrombosis was calculated in men, women with reproductive risk factors and women without reproductive risk factors at the time of their first venous thrombosis. F9 Malmö was genotyped and carriers and non-carriers contrasted., Results: In total, 2185 patients with a first venous thrombosis, 1043 men and 1142 women, were included. Overall, men had a 2.8-fold (95% confidence interval [CI], 2.2-3.4) higher risk of recurrent venous thrombosis than women. This risk was 5.2-fold (95% CI, 3.5-7.7) higher in men than in women with reproductive risk factors, and 2.3-fold (95% CI, 1.7-3.2) higher in men than in women without reproductive risk factors. No difference in risk of recurrence was found for carriers vs. non-carriers of F9 Malmö., Conclusion: Men experienced a recurrent venous thrombosis twice as often as women without reproductive risk factors. These findings indicate that men have a higher intrinsic risk of venous thrombosis than women, which is partly masked by female reproductive risk factors. The sex difference cannot be explained by F9 Malmö., (© 2015 International Society on Thrombosis and Haemostasis.)

We have previously shown that standardisation and normalization of results improve the intercentre variability of the calibrated automated thrombin generation test (TGT). We suspected that the source of reference plasma (RP) might be a contributing factor to variability and compared 5 commercial RP and a RP provided by the NIBSC, in an international, multicentre study. The detailed composition of the 6 tested plasma samples was determined in the Haemostasis Laboratory in Lyon. The lot to lot consistency, intra-assay, inter-assay variability were calculated for all tested plasmas. The RP and 3 plasma samples (a normal control, a hypocoagulable and a hypercoagulable plasmas) were tested over 6 days, in 5 European centres. Results were normalised against each of the tested RP and intercentre variability of results was compared. All laboratories used the same reagents. Before normalization, the inter-centre variability was 19.8 to 27.3%. After normalization, we observed a significantly improved inter-laboratory variation with all tested RP, despite differences between them. These results clearly demonstrate that the inter-centre variability of TGT can be significantly reduced by using a reference plasma normalization, and that certain RP have a better capacity to reduce this variability than others., ((c) 2009 Elsevier Ltd. All rights reserved.)