Preliminary Performances of A NEW Generation Assay : VIDAS D-Dimer Exclusion II.

Abstract 4203

The diagnostic value of D-dimer (DD) in the exclusion of deep venous thrombosis (DVT) and pulmonary embolism (PE) is well established. With more than 8,000 patients included in prospective management studies, VIDAS D-Dimer assays have been the most extensively assay studied. The aim of this study is to evaluate the analytical performances of a new generation of D-Dimer assay on the VIDAS instrument: VIDAS D-Dimer Exclusion II* (bioMérieux, Marcy l'Etoile, France). VIDAS D-Dimer Exclusion II (DEX2) assay principle combines a two-step enzyme immunoassay sandwich method with a final fluorescent detection. Total duration of the test is 20 minutes. Calibration is performed once every 28 days with one standard. Calibrator and controls (n=2) are reconstituted with distilled water. VIDAS D-Dimer Exclusion II has been calibrated against a panel of human plasma samples, the concentrations of which have been determined using the VIDAS D-Dimer Exclusion kit (DD2).

Studies were conducted to verify analytical performances of the new assay. Precision studies were performed according to CLSI document EP5-A2 using five plasma samples covering the range of the assay. The total %CV observed was less than 7%, including for those values around the areas of clinical decision limits. Limit of blank (LoB), limit of detection (LoD) and limit of quantification (LoQ) were evaluated according to CLSI document EP17-A and they were found at 7.41, 16.47 and 29 ng/mL (FEU) respectively. Linearity from a range of 45 to 10,000 ng/mL (FEU) has been determined on plasmas according to the recommendations of CLSI document EP6-A. Deviation from linearity was found to be less than 11%. Studies were conducted to verify the performance of the assay on potentially interfering substances such as bilirubin, triglycerides, hemoglobin, human albumin, and 47 commonly used drugs and anticoagulants. Less than 10% or 12% interference was observed at 500 and 7500 ng/mL (FEU) or 250 ng/mL (FEU) levels respectively, for each interfering substance. The assay Reference Interval was determined by testing 215 citrated plasma samples obtained from healthy volunteers; 90% of those values were found to be below the clinical cut off of 500 ng/mL (FEU). A method comparison study was performed on 584 citrated samples according to the recommendations of CLSI document EP9-A2. Regression line between VIDAS D-Dimer Exclusion II (DEX2) and VIDAS D-Dimer Exclusion (DD2) was: DEX2 = 1.04 x DD2 – 20,74. Observed bias was –4.53%, -0.38% and 3.07% at 250, 500 and 3000ng/mL (FEU) respectively.

In conclusion, VIDAS D-Dimer Exclusion II (DEX2) assay demonstrated good performance characteristics, particularly around the clinical cut off, as well as an excellent overall agreement with the extensively studied and published prior generation assay, VIDAS D-Dimer Exclusion (DD2). With the ability to provide results in 20 minutes and with optimized total precision, VIDAS D-Dimer Exclusion II assay (DEX2) will play a key role in the laboratory to provide accurate, rapid and reliable answers to clinicians.

* Product not cleared for use in the USA