Deep vein thrombosis and pulmonary embolism: a prospective, observational study to evaluate diagnostic performance of the Tina-quant D-Dimer Gen.2 assay.

Background: D-Dimer testing is a diagnostic tool for exclusion of deep vein thrombosis (DVT) and pulmonary embolism (PE). This study evaluated the diagnostic performance of the Tina-quant® D-Dimer Gen.2 assay (Roche Diagnostics International Ltd, Rotkreuz, Switzerland) in patients with low/intermediate pre-test probability of DVT/PE using standard, age-, and clinical probability-adjusted cut-offs. Methods: In this prospective, observational, multicenter study (July 2017-August 2019), plasma samples were collected from hospital emergency departments and specialist referral centers. DVT/PE was diagnosed under hospital standard procedures and imaging protocols. A standard D-dimer cut-off of 0.5 µg fibrinogen equivalent units (FEU)/ml was combined with the three-level Wells score; cut-offs adjusted for age (age × 0.01 µg FEU/ml for patients >50 years) and clinical probability (1 µg FEU/ml for low probability) were also evaluated. An assay comparison was conducted in a subset of samples using the Tina-quant D-Dimer Gen.2 assay and the previously established routine laboratory assay, STA-Liatest D-Di Plus assay (Stago Deutschland GmbH, Düsseldorf, Germany). Results: 2,897 patients were enrolled; 2,516 completed the study (DVT cohort: 1,741 PE cohort: 775). Clinical assessment plus D-dimer testing using the standard cut-off resulted in 317 (DVT) and 230 (PE) false positives, and zero (DVT) and one (PE) false negatives. Negative predictive value (NPV) was 100.0% (95% confidence interval [CI]: 99.7%-100.0%) and 99.8% (95% CI: 98.8%-100.0%) for DVT and PE, respectively. After age-adjustment, NPV was 99.9% (95% CI: 99.6%-100.0%) and 99.1% (95% CI: 97.8-99.7) for DVT and PE, respectively. False positive rates decreased (>50%) in clinical probability-adjusted analyses vs. primary analysis. In the assay comparison, the performances of the two assays were comparable. Conclusion: The Tina-quant D-Dimer Gen.2 assay and standard D-dimer cut-off level combined with the three-level Wells score accurately identified patients with a very low probability of DVT/PE.

Performance of 6 routine coagulation assays on the new Roche Cobas t711 analyzer.

OBJECTIVES: For new analyzers or tests, analytical evaluation is required before implementation in the clinical laboratory. We evaluated the novel Roche Cobas t711 analyzer with six newly developed coagulation assays: the activated partial thromboplastin time (aPTT), prothrombin time (PT), international normalized ratio (INR), fibrinogen, d-dimer and anti-Xa. The evaluation included imprecision experiments, method comparison with the currently used Stago STA-R Evolution, monitoring of unfractionated heparin (UFH) with aPTT, a fast centrifugation protocol to improve turn-around time, and determination of sample stability in whole blood and plasma. DESIGN AND METHODS: Imprecision and method comparison were assessed using commercial quality control samples and patient samples, respectively. For dose monitoring of UFH with the aPTT, samples from patients treated with UFH were used. Samples from healthy volunteers were collected for evaluation of the fast centrifugation protocol (5' 2750×g) and for investigating sample stability over 6-8 h. RESULTS: Results for between-run precision were within the desirable specification. Method comparison showed an excellent agreement for fibrinogen, d-dimer and anti-Xa. For aPTT, PT and INR, a good correlation was found, but results were significantly lower on the t711 compared to the STA-R Evolution, which is caused by different coagulation activators. Results from the fast centrifugation protocol differed not significantly from the standard protocol (15' 2500×g). Blood and plasma samples were stable at room temperature up to 6 and 8 h, respectively. CONCLUSIONS: The t711 coagulation analyzer with 6 novel tests is suitable for routine use in clinical laboratories.

Evaluating the analytical performance of four new coagulation assays for the measurement of fibrinogen, D-dimer and thrombin time.

INTRODUCTION: New laboratory methods to measure haemostatic function require careful assessment before routine use. We evaluated the analytical performance of four new coagulation assays for the measurement of fibrinogen by Clauss assay, prothrombin time-derived fibrinogen, thrombin time and D-dimer levels. METHODS: The four assays were evaluated on the cobas t 711 and cobas t 511 analysers at four centres in Europe. Analytical performance and method comparisons with other commercially available assays were performed according to Clinical and Laboratory Standards Institute guidelines (EP09-A3, EP05-A3) using residual anonymized human sodium citrate (3.2% [0.109M]) plasma samples. Lot-to-lot variability and the equivalency of each assay on the cobas t 711 and cobas t 511 analysers were also assessed. RESULTS: Overall, coefficients of variance were ≤4.1% and ≤8.6% for within-run precision and total reproducibility, respectively. Method comparison experiments showed good or acceptable agreement for each assay compared with their respective comparator method, and equivalency was demonstrated for the two cobas t platforms (Pearson's correlation coefficient ≥0.991). A high level of consistency was observed between lots for all four assays (Pearson's correlation coefficient ≥0.994). CONCLUSION: This multicentre study demonstrates excellent analytical performance for four new coagulation assays on the cobas t 711 and cobas t 511 analysers.