No abstract

The measurement of the specific fibrin degradation products D-dimer is widely used in the diagnostic work-up of pulmonary embolism (PE) and venous thromboembolism in general. Due to the heterogeneity of D-dimer assays, it is now recommended that the performances of each new D-dimer assay have to be evaluated in clinical trials. The HemosIL D-Dimer HS assay (Instrumentation Laboratory, Paris, France) is a new rapid quantitative latex-microparticle agglutination-based assay which is automated on the ACL TOP analyzer (Instrumentation Laboratory). Latex microparticles were sensitized with the F(ab')2 fragment of a monoclonal antibody directed against D-dimer. The change in optical density at 671nm was recorded after addition of the plasma sample (16µL) and test result is usually obtained within 4 minutes. Test result is expressed in ng/mL (D-dimer) and the reference range in the normal population was 0-243 ng/mL as defined by the reagent manufacturer. Its within run precision (n=20) and its between run precision (n=8) were found to be below 7.0% using commercially available lyophilized plasma samples both in the subnormal and abnormal ranges of concentrations. The aim of the present study was to evaluate the performances in the diagnosis of PE and to compare with those of two other automated quantitative assays i.e. the HemosIL D-dimer assay (Instrumentation Laboratory) and the VIDAS D-dimer Exclusion assay (BioMérieux, Marcy l'Etoile, France). All three assays were performed according to the recommendations of the manufacturers, and the cut-off levels used were those reported in the literature and/or the package inserts of the assay kits i.e. 230 ng/mL for the HemosIL D-Dimer HS and the HemosIl D-Dimer assays and 500 ng/mL (FEU) for the Vidas D-Dimer Exclusion assay. We prospectively studied consecutive outpatients with chest pain and suspected PE (low and moderate pre-test probability) referred to the emergency ward of our Institution (University hospital). The preliminary results presented here corresponded to those of 166 patients referred during a 3-month period. The diagnosis of PE was retained in 12 cases (7.2%). The result of the 3 tested assays was found above the clinically defined cut-off level in all of these 12 patients with PE, leading to a sensitivity and a negative predictive value (NPV) of 100%. The result of the HemosIL D-Dimer HS assay was found to be above the cut-off level in 111 of the 155 patients without PE (72%). Similarly, D-dimer levels were found above the cut-off in 76% of these patients when evaluated with the HemosIL D-dimer and in 75% with the Vidas D-dimer Exclusion assay. The high proportion of elevated D-dimer levels in our series was related to the demographical characteristics of the studied population (mean age=72.5 years, range: 23-96). The specificity of the HemosIL DDimer HS assay was found to be higher than those of the two other quantitative assays. In conclusion, the HemosIL D-dimer HS assay allowed an accurate diagnosis of all of the patients with PE and so, could be valid...