Summary. Background: Little information is available on the epidemiology of venous thromboembolism (VTE) in Asian populations. Objectives: To investigate VTE incidence, VTE cumulative recurrence rates and risk factors for VTE recurrence among the adult Taiwanese population. Methods: This population-based cohort study used the Taiwanese National Health Insurance claims databases to identify 5347 adult patients (2463 men, 46.1%) with VTE diagnosed in 2001 and 2002. We calculated the crude incidence of VTE and its recurrence. We also conducted a nested case-control study (n = 3576) among this population to estimate the association between VTE recurrence and exposure to potential VTE risk factors by conditional logistic regression. Results: The crude incidence of VTE was 15.9 per 100 000 person-years, and its recurrence rate was 5.1% per person-year. During 11 566 person-years of follow-up, the cumulative rates of VTE recurrence at 6, 12, 24, 36 and 47 months were 6.7%, 9.4%, 12.4%, 13.9%, and 14.4%, respectively. By conditional logistic regression, histories of VTE [adjusted odds ratio (OR) 1.71, 95% confidence interval (CI) 1.32-2.16] or malignant neoplasm (adjusted OR 1.64, 95% CI 1.26-1.99), major extremity trauma (adjusted OR 2.76, 95% CI 1.82-4.52), serious neurologic diseases (adjusted OR 1.43, 95% CI 1.12-1.84) or undergoing major surgery (adjusted OR 4.57, were associated with higher risks of VTE recurrence. Conclusions: The incidence of VTE is lower in the Taiwanese population than in Caucasians. Most VTE recurrences occur within 12 months, but they continue to occur beyond 1 year. The VTE recurrences are associated with malignancy, history of VTE, and major surgery after a previous VTE.

Summary.  Background: Thromboprophylaxis should be universally administered in major orthopedic surgery. However, epidemiology of venous thromboembolism (VTE) following major knee surgery in Asia is scarce. Objective: To describe the use of thromboprophylaxis and calculate the incidence and risk factors of symptomatic VTE following major knee surgery in Taiwan. Methods: We used Taiwan’s National Health Insurance Research Database to retrospectively identify patients (≧45 years) who underwent major knee surgery from 1998 to 2007 and collected the medical records within 3 months after the discharge. Logistic regression analysis was used to determine the risk factors of symptomatic VTE after the surgery. Results: We identified 113 844 patients (mean age, 69.0 ± 7.7 years; female, 75.2%) receiving major knee arthroplasties. The mean length of stay was 9.1 ± 3.3 days. The overall pharmacological thromboprophylaxis rate was 2.2%. The 3‐month cumulative incidence of procedure‐related symptomatic VTE was 0.46% (95% CI, 0.42–0.50%). The median time to the first post‐operation VTE was 7 days, with 85.4% occurring within 2 weeks after the discharge. Logistic regression analysis showed that previous VTE, malignancy, heart failure and neurologic disorder with extremity paralysis or pararesis were independent risk factors (P < 0.05) for symptomatic VTE following major knee arthroplasties. Conclusions: The thromboprophylaxis rate is low, which may be due to the very low incidence of symptomatic VTE after the surgery in Taiwan. Most symptomatic VTE occurred within 2 weeks after the surgery. Universal thromboprophylaxis for knee arthroplasties may not be necessary in Taiwan, but it should be considered in some high‐risk populations.