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D-dimer vs ultrasound for DVT: use prediction rule

Clinical Question:
Is d-dimer testing always necessary in patients with possible deep vein thrombosis?

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

Reference:
Linkins LA, Bates SM, Lang E, et al. Selective d-dimer testing for diagnosis of a first suspected episode of deep vein thrombosis. A randomized trial. Ann Intern Med 2013;158(2):93-100.  [PMID:23318311]

Study Design:
Diagnostic test evaluation

Funding:
Foundation

Setting:
Outpatient (any)

Synopsis:
The Canadian researchers enrolled 1732 consecutive patients presenting with a suspected first DVT. The patients were randomly assigned, using concealed allocation, to receive either usual testing or selective testing. In the usual testing group, all patients had d-dimer testing; if positive, the affected leg was examined by ultrasound. 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 ultrasound evaluation. Patients at high probability, and all inpatients, underwent ultrasound without initial d-dimer testing. All study participants were followed up for 3 months, and clinical results were similar in both groups. The selective testing approach decreased d-dimer testing in 1 of every 5 patients (21.8 percentage points; 95% CI, 19.1 - 24.8) and decreased the overall proportion who required ultrasound by 7.6 percentage points (2.9 - 12.2).

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