Effectiveness of Management of Suspected Deep Vein Thrombosis in General Practice Based on a Clinical Decision Rule Including a Point of Care D-dimer Test.

Prior studies have evaluated the safety and effectiveness of a diagnostic work up based on combined use of a clinical decision rule and a D-dimer laboratory test in patients with suspected deep vein thrombosis in secondary care facilities. The overall outcome of these studies show that approximately 30% of additional objective evaluation can be avoided without compromising the safety, resulting in failure rates of less than 1%. The objective of our study was to assess the effectiveness of a modified algorithm using a dichotomized clinical decision rule including a point of care D-dimer test in patients suspected of deep vein thrombosis in primary care. The AMUSE study is a prospective cohort study of consecutive patients with clinically suspected acute deep vein thrombosis conducted in 400 general practices coordinated by 3 university affiliated centers in the Netherlands from March 2004 through January 2007. The study population of 1029 patients included 63% women. Patients were categorized as “deep vein thrombosis unlikely” or “deep vein thrombosis likely” using a dichotomized version of a for general practice adapted clinical decision rule based on the Wells rule. Patients classified as unlikely were excluded from further testing. All other patients underwent ultrasonography. Anticoagulants were withheld from patients classified as unlikely. All patients were followed up for 3 months. The main outcome measure was symptomatic or fatal venous thromboembolism (VTE) during 3 months follow-up. Deep vein thrombosis was classified as unlikely in 500 patients (48.6%), all of whom were not treated with anticoagulants; subsequent non fatal VTE occurred in 8 patients (1.6% [95 CI 0.7–3.1%]). In 500 patients categorized as likely, deep vein thrombosis was confirmed in 124 patients (24.8%), 3 patients did not receive objective testing (0.6%) and 373 patients were tested negative (74.6%). Two out of 4 patients not receiving objective testing had confirmed deep vein thrombosis in the 3 month follow-up period. In patients that tested negative 4 non fatal events occurred during the 3 month follow-up (1.1%). The algorithm was completed and allowed a management decision in 97.2% of patients. We conclude that this management strategy is both safe and highly effective in patients with suspected deep vein thrombosis in general practice. Its use is associated with low risk for subsequent fatal and nonfatal VTE and a further increase in the yield of objective diagnostic tests.