Clinical Question

Is d-dimer testing always necessary in patients with possible deep venous thrombosis (DVT)?

Bottom Line

Use the Wells criteria to determine the likelihood of deep venous thrombosis; patients at moderate to high risk should go straight to ultrasonography. Patients at low risk should have d-dimer testing, followed by ultrasonography only if the results are positive. This approach decreases the use of d-dimer testing, as well as the need for ultrasonography, while producing the same clinical results. (Level of Evidence = 1b)

Synopsis

The Canadian researchers enrolled 1,732 consecutive patients presenting with a suspected first DVT. The patients were randomly assigned, using concealed allocation, to receive usual testing or selective testing. In the usual testing group, all patients had d-dimer testing; if positive, the affected leg was examined by ultrasonography. In the selective testing group, patients were evaluated based on their pretest probability of DVT, calculated using the Wells clinical prediction rule. Patients at low or moderate risk of DVT underwent d-dimer testing and, if results were positive, had ultrasonography evaluation. Patients with high probability, and all inpatients, underwent ultrasonography without initial d-dimer testing.

All study participants were followed for three months, and clinical results were similar in both groups. The selective testing approach decreased d-dimer testing in one of every five patients (21.8 percentage points; 95% confidence interval, 19.1 to 24.8) and decreased the overall proportion who required ultrasonography by 7.6 percentage points (95% confidence interval, 2.9 to 12.2).

Reference

LinkinsLABatesSMLangEet alSelective d-dimer testing for diagnosis of a first suspected episode of deep venous thrombosis: a randomized trial. Ann Intern Med.2013; 158( 2): 93– 100.

Study design: Diagnostic test evaluation

Funding source: Foundation

Allocation: Concealed

Setting: Outpatient (any)