The Worcester Venous Thromboembolism Study: A Population-Based Study of the Clinical Epidemiology of Venous Thromboembolism


None of the authors have any conflicts of interest to declare. Address correspondence and requests for reprints to Dr. Spencer: Department of Medicine, McMaster University – Faculty of Health Sciences, 1200 Main Street West, Hamilton, ON L8N 3Z5 (e-mail:


BACKGROUND: While there have been marked advances in diagnostic and therapeutic strategies for venous thromboembolism, our understanding of its clinical epidemiology is based on studies conducted more than a decade ago.

OBJECTIVE: The purpose of this observational study was to describe the incidence and attack rates of venous thromboembolism in residents of the Worcester Statistical Metropolitan Area in 1999. We also describe demographic and clinical characteristics, management strategies, and associated hospital and 30-day outcomes.

DESIGN AND MEASUREMENTS: The medical records of all residents from Worcester, MA (2000 census=477,800), diagnosed with International Classification of Diseases, 9th revision (ICD-9) codes consistent with possible venous thromboembolism during 1999 were independently validated, classified, and reviewed by trained abstractors.

RESULTS: A total of 587 subjects were enrolled with validated venous thromboembolism. The incidence and attack rates of venous thromboembolism were 104 and 128 per 100,000 population, respectively. Three quarters of patients developed their venous thromboembolism in the outpatient setting – a substantial proportion of these patients had undergone recent surgery or had a recent prior hospitalization. Less than half of the patients received anticoagulant prophylaxis during high-risk periods before their venous thromboembolism. Thirty-day rates of venous thromboembolism recurrence, major bleeding, and mortality were 4.8%, 7.7%, and 6.6%, respectively.

CONCLUSION: These data provide insights into recent incidence and attack rates, changing patient profiles, management strategies, and subsequent outcomes in patients with venous thromboembolism. The underutilization of prophylaxis before venous thromboembolism, and relatively high 30-day recurrence rates, suggest a continued need for the improvement of venous thromboembolism prophylaxis and management in the community.