Comparison of the clinical usefulness of two quantitative D-Dimer tests in patients with a low clinical probability of Pulmonary Embolism R. Karami Djurabi a , F.A. Klok a , M. Nijkeuter a , K. Kaasjager b , P.W. Kamphuisen c,f , M.H.H. Kramer d , M.J.H.A. Kruip e , F.W.G. Leebeek e , Harry R. Büller f , M.V. Huisman a, ⁎ a Section of Vascular Medicine, Department of General Internal Medicine - Endocrinology, Leiden University Medical Center, Leiden, the Netherlands b Department of Internal Medicine, Rijnstate Hospital, Arnhem c Department of General Internal Medicine, Radboud University Medical Center, Nijmegen d Department of Internal Medicine, VU University Medical Center, Amsterdam e Department of Hematology, Erasmus University Medical Center, Rotterdam f Department of Vascular Medicine, Academic Medical Center, Amsterdam abstract article info Article history: Received 29 May 2008 Received in revised form 14 July 2008 Accepted 29 July 2008 Available online 24 September 2008 Keywords: Pulmonary embolism D-dimer Clinical utility Efficacy Safety Background: Quantitative D-Dimer tests are established methods in the non-invasive diagnostic management to rule out venous thromboembolism (VTE). The diagnostic performance and the clinical efficiency different D-Dimer assays in the exclusion of pulmonary embolism (PE) have not yet been compared in a clinical outcome study. Objective: Evaluation of the efficiency and safety of excluding the diagnosis of PE with two different quantitative D-Dimer assays in consecutive patients with clinically suspected PE. Patients and Methods: We studied the VTE-failure rate of 2206 consecutive patients with an unlikely clinical probability in whom VIDAS or Tinaquant D-Dimer tests were performed. Results: The prevalence of PE in 1238 patients whose D-Dimer level was analyzed with Tinaquant assay was 11%. The VIDAS assay group consisted of 968 patients with a PE prevalence of 13%. The VIDAS assay had a sensitivity of 99.2% (95%CI; 96- N 99.9%), the Tinaquant assay of 97.3% (95%CI; 93 -99%). The negative predictive value (NPV) in the Tinaquant assay group was 99.4% (95%CI 98-99.8%) in comparison to 99.7% (95%CI 99-N 99.9%) in the VIDAS assay group. During 3 month of follow-up, there were no fatal cases of PE among patients with normal D-Dimer and unlikely clinical probability in both D-Dimer assay groups. In addition, the test efficiency of Tinaquant assay was significantly higher in comparison to VIDAS assay (52% vs 42%, p b 0.001). Conclusion: Both Tinaquant and VIDAS D-Dimer tests perform equally well in combination with an unlikely clinical probability in excluding PE. The Tinaquant test was shown to be more efficient. © 2008 Elsevier Ltd. All rights reserved. Introduction D-Dimer assays have an established role in the diagnostic approach of venous thrombo-embolism. D-Dimer test in combination with the determination of clinical pretest probability is increasingly accepted as a first-line test in patients with suspected pulmonary embolism (PE) [1–6]. Several management studies have shown that PE can be safely ruled out without the need for additional imaging in patients with an unlikely clinical pretest probability according to Wells (Table 1) and a normal D- Dimer test result, occurring in 20% to 40% of patients [6–8]. When choosing a specific D-Dimer test, it is important to consider both sensitivity and specificity of the assay. Most quantitative D- Dimer tests are very sensitive but specificity is generally relatively poor [9], so that a normal result has high negative predictive value but occurs in a relatively small proportion of patients. Differences between D-Dimer assays are caused by antibody specificity, especially concerning the preference for high- or low-molecular-weight fibrin derivates and for cross-linked and non-cross-linked fibrin derivates [10]. Other causes of discrepancies between D-Dimer assays are thought to be the time-dependency of neo-epitope expression in the course of fibrin formation and dissolution, assay format, purity or heterogeneity of the calibrator, matrix effects of plasma on epitope presentation and interference by irrelevant analysis [11]. Importantly, although there is a wealth of studies evaluating different D-Dimer tests in the setting of venous thrombosis and Thrombosis Research 123 (2009) 771–774 Abbreviations: VTE, Venous thromboembolism; PE, Pulmonary embolism; DVT, Deep vein thrombosis; CT, Computed tomography; CUS, Compression ultrasonography; CI, Confidence interval; ROC, Receiver operator curve; AUC, Area under the curve; NPV, Negative predictive value. ⁎ Corresponding author. LUMC (C4-70), Albinusdreef 2, Postbus 9600, 2300 RC Leiden, The Netherlands. Tel.: +31 71 5262085; fax: +31 71 5248140. E-mail address: M.V.Huisman@LUMC.nl (M.V. Huisman). 0049-3848/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2008.07.014 Contents lists available at ScienceDirect Thrombosis Research journal homepage: www.elsevier.com/locate/thromres Regular Article