Comparison of quantitative immunoturbidimetric and semiquantitative latex-agglutination assays for D-dimer measurement in canine plasma.

Background: D-dimer measurement in dogs is considered the most reliable test for detecting disseminated intravascular coagulation or thromboembolism. Objectives: The purposes of this study were to compare 2 D-dimer assays, a quantitative immunoturbidimetric and a semiquantitative latex agglutination assay, and to assess the effect of hemolysis and storage conditions on D-dimer concentration using the quantitative assay. Methods: The immunoturbidimetric assay was validated using canine citrated plasma samples containing different concentrations of D-dimer. The effect of storage at various temperatures and times was assessed. Hemolysis was produced by adding lysed RBCs to the samples for a final hemoglobin concentration of 0.35 g/dL. Results: For clinically relevant values (>250 μg/L), intra-assay and interassay coefficients of variation were 6.8% and 7.2%. The assay was linear (r2=1.00), and the tests had good agreement (κ=0.685, P<.001). Storage at 4 °C and −20 °C and hemolysis had no significant effect on D-dimer concentrations. In hemolyzed samples stored at room temperature for ≥48 hours, fine clots were noted and often resulted in falsely increased D-dimer concentrations. Conclusions: Our findings suggest that the immunoturbidimetric assay validated in this study is reliable and accurate for the measurement of D-dimer in canine plasma. Samples can be stored for up to 1 month at −20 °C and moderate hemolysis does not significantly affect the D-dimer concentration in frozen or refrigerated samples.