Assessment of D-dimer measurement by ELISA or latex methods in deep vein thrombosis diagnosed by ultrasonic duplex scanning

Abstract

In 100 consecutive patients with clinically suspected deep vein thrombosis (DVT) of the legs, plasma D-dimer measurements based on an enzyme linked immunosorbent assay (ELISA) and on latex agglutination (Diagnostica Stago) were compared to the results of real time B mode ultrasound imaging combined with Doppler examination, which in a previous study has proved to be a very accurate method competitive with venography for the diagnosis of DVT. Forty five patients had DVT identified with the ultrasonic tests. We have obtained for ELISA and latex tests of D-dimer respectively: accuracy: 60%, 56%; sensitivity: 98%, 98%; specificity: 29%, 22%; predictive value of a positive test: 53%, 50% and predictive value of a negative test: 94%, 92%. These results confirmed those of previous studies using ELISA or latex assays, with venography as a reference test. We conclude that a negative D-dimer test, defined by a value lower than 0.5 μg/ml, excludes the diagnosis of DVT in 94% of cases by ELISA method and in 92% of cases by latex method. A reduction of venography or other objective testing of the venous circulation could be obtained if these methods were not performed in the case of a negative D-dimer test. However the safety of withholding anticoagulant therapy in out patients with negative tests needs confirmation in a prospective trial.