The value of rapid D-dimer testing combined with structured clinical evaluation for the diagnosis of deep vein thrombosis.

PURPOSE

Large studies have shown that most cases referred for duplex sonography for suspected deep vein thrombosis (DVT) have normal scan results. For medical and economic reasons, a preselection procedure, which allows the detection of true-negative cases before duplex scanning, is required; this procedure should be characterized by a high sensitivity and a high negative predictive value.

METHODS

In 343 patients (398 lower extremities) with suspected DVT, the DVT probability was clinically assessed, and a whole blood D-dimer agglutination test and a duplex scan were performed. The diagnostic sensitivities of the D-dimer test alone, a high clinical DVT probability alone, and the combination of both were evaluated.

RESULTS

The sensitivity values for the D-dimer test to diagnose proximal and distal DVTs were 88.7% and 80.9%, the negative predictive values (NPV) were 96.3% and 97.9%, and the specificity and the positive predictive value (PPV) were 54.8% and 49.6% and 26.6% and 8.2%, respectively. The sensitivities of the clinical DVT probability assessment for the diagnosis of proximal and distal DVTs were 83.9% and 66.7%, respectively; the corresponding NPVs were 94.9% and 96.5%, respectively. The specificity was 56.1% and 50.8%, and the PPVs were 26.1% and 7.0%, respectively. The combined use of the results of the clinical probability assessment and the D-dimer test resulted in sensitivities for proximal and distal DVTs of 98.4% and 90.5%, NPVs of 99.3% and 98.6%, a specificity of 43.4% and 38.4%, and PPVs of 24. 3% and 7.6%, respectively.

CONCLUSION

The combined use of a clinical DVT probability assessment scheme and the D-dimer test largely avoids false negative results, has a high sensitivity and NPV, helps to reduce the costs of DVT diagnosis, and may, in the future, be useful as a preselection procedure before duplex sonography.