P1697: EVALUATION OF THE DIAGNOSTIC PERFORMANCE OF THE TINA-QUANT D-DIMER GEN. 2 IN PATIENTS WITH SUSPECTED DEEP VEIN THROMBOSIS

Abstract

Background: Combined with clinical pretest probability evaluation, D-dimer is a central element in the diagnostic work-up of suspected deep vein thrombosis (DVT). Different assays are available for the measurement of D-dimer. However, D-dimer assays are not standardized and the results are not comparable among the different assays. Therefore, the cut-off used to discriminate between positive and negative test results should be evaluated assay-wise in each institution. According to our best knowledge, only one study has evaluated the diagnostic performance of Tina-quant D-Dimer Gen. 2 assay in proximal DVT, and this study excluded patients with recurrent DVT. Aims: The aim of our study was to evaluate the diagnostic performance of the Tina-quant D-Dimer Gen. 2 assay (Roche Diagnostics) in the exclusion of all types of DVT, and to compare its performance with the STA-Liatest D-Di Plus (Stago). Methods: In the Ri-Schedule study (Rivaroxaban for Scheduled Work-up of Deep Vein Thrombosis; NCT 02486445), which was a prospective outcome study, D-dimer was measured with STA-Liatest D-Di Plus in 1653 adult patients referred to the Emergency Department at Østfold Hospital with suspected DVT. Exclusion criteria were failure to consent, and previous inclusion in the Ri-Schedule study within the past 3 months. Patients with D-dimer levels ≥ 0.5 µg/mL fibrinogen equivalent units (FEU) were referred to whole-leg compression ultrasonography (CUS) to confirm/exclude the DVT diagnosis. All patients were followed up after 90 days. To evaluate the diagnostic performance of the Tina-quant D-Dimer Gen. 2 assay, stored frozen plasma samples acquired from 1097 patient in the Ri-Schedule study were analyzed on Cobas t711. These samples were withdrawn simultaneously as the sample that were analyzed with the STA-Liatest D-Di Plus on STA-R. The diagnostic performance of the two assays were depicted and compared using test performance parameters and ROC curve. Results: Of the 1097 patients, 730 patients had a positive D-dimer with the Tina-quant D-Dimer Gen. 2, and 775 patients had a positive D-dimer with the STA-Liatest D-Di Plus; cut-off for both tests was ≥ 0.5 µg/mL FEU. DVT diagnosis was confirmed in 210 (19.2%) by CUS examination. The sensitivity and negative predictive value (NPV) for the Tina-quant D-Dimer Gen. 2 assay were 96.2% (95% CI 92.6–98.3) and 97.8% (95% CI 95.8–98.9) respectively; the specificity and positive predictive value (PPV) were 40.5% (95% 37.2–43.8) and 27.7% (95% CI 26.5–28.9) respectively (Table 1). The sensitivity and NPV for the STA-Liatest D-Di Plus assay were 98.1% (95% CI 95.2–99.5) and 98.8% (95% CI 96.8–99.5) respectively (Table 1). ROC curve analysis showed an AUC of 0.85 for both assays, with no significant differences between the assays. Of those with D-dimer value below the cut-off, 8 patients had DVT diagnosed by CUS at time of initial work up or during the subsequent 90 day with Tina-quant as compared with STA-D-Di Plus. Image:Summary/Conclusion: The Tina-quant D-Dimer Gen. 2 assay on Cobas t711 showed an overall good and comparable performance for the exclusion of DVT when compared with STA-Liatest D-Di Plus assay.