Methods Cohort study of exposed and unexposed patients nested in the OPTIMEV multicentre observational study (Clinical Trials NCT00670540) Constitution of the OPTIMEV cohort: From November 2004 to January 2006, 8256 patients with a suspicion of symptomatic VTE (lower and upper extremity DVT, PE) were enrolled and benefited from objective tests to confirm or rule out the suspicion of VTE. This included a bilateral whole leg compression CUS for all cases of suspicion of DVT; Baseline characteristics including patient's demographics, signs, symptoms & risk factors for VTE, venous status, results of objective tests and treatments were prospectively collected in an electronic case report form.