Cost-effective strategies for the identification of subjects at risk of venous thromboembolism (VTE) in the active population are still lacking. Our objectives were to identify risk factors for venous thromboembolism in active subjects. We analyzed data from a population-based sample of 15 055 Caucasians aged 18–65 years randomly selected from the census list of the township of Vicenza, Italy. A validated methodology was used to retrospectively identify subjects with previous VTE. Body mass index (BMI), smoking, oral contraceptive use, previous superficial vein thrombophlebitis (SVT) and familial history of VTE, all at the age of first thrombosis, were ascertained by direct interview and by review of available medical records. Ninety-two deep vein thromboses [prevalence: 61.1/10 000, 95% confidence interval (CI) 49.2–74.9], three upper deep vein thrombosis (prevalence: 1.9/10 000, 95% CI 0.4–5.8) and 21 pulmonary embolism (prevalence: 13.9/10 000, 95% CI 8.6–21.3) were identified. After age and sex adjustment, clinically identifiable risk factors were: history of SVT [odds ratio (OR) = 6.8], oral contraceptive use (OR = 4.7), family history of VTE (OR = 4.5), smoking (OR = 1.7) and BMI above the third tertile (OR vs. mid-tertile 2.9). While previous SVT and BMI were associated with VTE in all circumstantial situations (surgery/trauma, pregnancy or idiopathic VTE), for oral contraceptive use, positive family history and smoking the degree of association varied significantly depending on the situation. Non-fatal VTE affects 0.7% of the subjects belonging to an active population, 56% of cases being potentially preventable. In 30% of VTE cases, at least two easily recognizable risk factors are present. Clinical assessment of risk factors remains the mainstay of VTE prevention.
