Interference of blood plasma components in turbidimetric D-dimer estimation

Overview

Two immunoturbidimetric D-dimer assays were tested in terms of their resistance to plasma interferents. The Diagnostica Stago products STA LIATEST DDi and its new version STA LIATEST D-Di Plus were used to detect D-dimer concentrations in samples with confirmed presence of interferents. A solid phase immunoassay with fluorimetric detection VIDAS^® D-Dimer ExclusionTM was used as the reference method. In the group of 12 samples containing interferents false positivity was detected in all 12 cases during testing with the STA LIATEST DDi kit. Results using the STA LIATEST DDi Plus kit were falsely positive in 4 cases. A correlation study on plasma samples with a range of 70–12000 μg/l –⁠ FEU was carried out. The coefficient of correlation between both assays was R² = 0.9944. Precision studies of STA LIATEST DDi Plus were performed with the control samples on normal and pathological level. Intra-assay precision (expressed as coefficient of variation) was 7.38% on normal and 1.61% on pathological D-dimer levels. Inter-assay coefficient of variation values were 7.78% on the normal and 2.16% on the pathological D-dimer levels. The working range of the D-dimer concentration of STA LIATEST DDi Plus is up to 20000 μg/l–FEU. An increased resistance of the STA LIATEST DDi Plus to interferents was demonstrated.

Keywords:
D-dimer, thrombosis, matrix effect, rheumatoid factor, immunochemical diagnostics