Rapid D-dimer testing and pre-test clinical probability in the exclusion of deep venous thrombosis in symptomatic outpatients

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Abstract
We assessed the performance of three rapid D-dimer tests (Auto Dimertest®, VIDAS® and Tinaquant®) in combination with a pre-test clinical probability model for deep venous thrombosis (DVT) in 106 consecutive outpatients with suspected DVT. Contrast venography or colour-coded duplex ultrasonography demonstrated the presence of DVT in 47 patients (14 distal DVT and 33 proximal DVT). First, we assessed the accuracy indices for different cut-off levels of the rapid D-dimer tests. Sensitivity was found to be 97.9–100%, negative predictive value (NPV) was 96.3–100%, and the exclusion rate was 24.5–31.1%. Next, the patients were grouped according to the pre-test clinical probability model in categories with low, moderate or high probability. In patients with a low pre-test probability, DVT would have been directly ruled out and the patients would not have undergone further investigations. In patients with a moderate probability, D-dimer testing and, in the case of a positive result, objective testing would have been performed and, in the case of a negative result, they would have been ruled out of having DVT. Patients with high probability would directly have undergone objective tests for DVT. The combination with the pre-test clinical probability model improved the exclusion rate (43.5–44.6%), whereas sensitivity (97.5–100%) and NPV (97.6–100%) remained roughly unchanged. The combination of rapid D-dimer tests with a pre-test clinical probability model may help to reduce unnecessary work-up in patients with suspected DVT.