Preliminary Evaluation of two New Rapid Immunoturbidimetric D-dimer Assays in Patients with Clinically Suspected Venous Thromboembolism (VTE)

Abstract

The practical utility and diagnostic accuracy of two new rapid, automated and quantitative immunoturbidimetric D-dimer methods have been evaluated in a population of 123 randomly selected patients with suspected VTE. The STA Liatest D-dimer and MDA D-dimer methods are based on the photo-optical measurement of the rate of agglutination of antibody-coated latex particles. The VIDAS D-dimer automated Elisa was used as the reference method. Diagnosis was confirmed in 51 patients (29 PE, 19 DVT, 3 DVT+PE). The immunoturbidimetric methods compared favorably with the VIDAS Elisa as judged from the correlation coefficients of linear regression lines (r = 0.82, MDA vs VIDAS; r = 0.75, STA vs VIDAS) and areas under the curve of ROC plots (VIDAS 0.83; STA 0.83; MDA 0.81). At a discriminant value of 500 ng/mL, all three D-dimer assays showed high sensitivity (96-98%), high NPV (93-97%) and moderate specificity (39-42%). Reproducibility of results around the cut-off is an important aspect of the diagnostic utility of D-dimer assays. CV's of duplicate determinations in this critical zone showed average values of 5.4% and 17.0% for MDA and STA, respectively. These data demonstrate that such rapid and automated latex-based methods for the quantitative measurement of D-dimer hold promise as reliable and cost-efficient approaches for the exclusion of VTE. Prospective patient management studies will be required to confirm this.