Different cut-off values of quantitative D-dimer methods to predict the risk of venous thromboembolism recurrence : a post-hoc analysis of the PROLONG study

Background: The PROLONG study showed that patients with venous thromboembolism who had qualitatively abnormal results in a D-dimer assay (Clearview Simplify D-dimer) after discontinuation of vitamin K antagonism benefit from resumption of treatment with vitamin K antagonism. The objective of this study was to evaluate the possible advantage of using quantitative D-dimer assays. Design and Methods: VIDAS D-dimer Exclusion (bioMerieux), Innovance D-DIMER (Dade Behring), HemosIL D-dimer HS (Instrumentation Laboratory) and STA Liatest D-dimer (Diagnostica Stago) assays were performed in plasma aliquots sampled 30±10 days after cessation of vitamin K antagonism in 321 patients enrolled in the PROLONG study. Results: During the follow-up without vitamin K antagonism, 25 patients had recurrent venous thromboembolism. The cut-off levels of the quantitative assays giving results most comparable with those of the qualitative test were: VIDAS = 800 ng/mL; Innovance = 800 ng/mL; HemosIL HS = 300 ng/mL; STA Liatest = 700 ng/mL. When the effect of the patients' age (≤70 vs. >70 years) was analyzed, it was found that only in younger patients was the rate of recurrence of venous thromboembolism significantly higher in patients with abnormal D-dimer levels. However, using the quantitative assays and age-specific cut-off levels it was possible to determine statistically significant hazard ratios also in elderly patients (VIDAS = 600 and 1200 ng/mL, Innovance = 500 and 900 ng/mL, HemosIL HS = 250 and 450 ng/mL, STA Liatest = 700 and 1000 ng/mL, in patients aged ≤70 and >70 years, respectively). Conclusions: Quantitative D-dimer assays may provide information useful for evaluating the individual risk of recurrent venous thromboembolism. They seem particularly advantageous since they allow the selection of different cut-off levels according to the age or other characteristics of the patients.