Performance of two latex D-dimer assays in suspected recurrent deep vein thrombosis of the lower limbs

Background : Diagnosing or excluding recurrent DVT remains a challenge. A good diagnostic accuracy of D-dimer measurement for the exclusion of recurrence has been reported. Depending on the clinical setting, D-dimer measurement may be performed on the day of patient presentation or the following day using stored plasma. Objective : To test the effect of plasma storage, at 4°C and –20°C for 24 hours, on D-dimer levels and to compare the performance of (MDA) and Tinaquant D-dimer assays in patients with suspicion of recurrent DVT. Methods : On the day of presentation, plasma obtained from 88 consecutive patients with suspected recurrent DVT was aliquoted and a) stored at 4oC and -20oC for 24 hours before measuring D-dimer with the MDA assay, and b) stored at –20oC and D-dimer measurements repeated using the Tinaquant assay. Results : Storage for 24 hours at 4oC and -20oC had little effect on D-dimer measurements when compared to measurements before storage, Kappa coefficient 0.87 (4oC) and 1.0 (-20o), respectively. A very good agreement was found between MDA and Tinaquant assay results with a Kappa coefficient of 0.83. Conclusion : Storage of plasma up to 24 hours at 4oC and -20oC does not affect the stability of the D-dimer levels. MDA and Tinaquant D-dimer assays show a very good agreement in classifying patients with suspected recurrent thrombosis as DVT positive or negative.