Diagnostic Accuracy and User-Friendliness of 5 Point-of-Care D-Dimer Tests for the Exclusion of Deep Vein Thrombosis Geert-Jan Geersing, 1 Diane B. Toll, 1 Kristel J.M. Janssen, 1 Ruud Oudega, 1 Marloes J.C. Blikman, 1 Rene ´ Wijland, 1 Karen M.K. de Vooght, 2 Arno W. Hoes, 1 and Karel G.M. Moons 1* BACKGROUND: Point-of-care D-dimer tests have re- cently been introduced to enable rapid exclusion of deep venous thrombosis (DVT) without the need to refer a patient for conventional laboratory-based D-dimer testing. Before implementation in practice, however, the diagnostic accuracy of each test should be validated. METHODS: We analyzed data of 577 prospectively iden- tified consecutive primary care patients suspected to have DVT, who underwent 5 point-of-care D-dimer tests— 4 quantitative (Vidas®, Pathfast™, Cardiac®, and Triage®) and 1 qualitative (Clearview Simplify®)—and ultrasonography as the reference method. We evalu- ated the tests for the accuracy of their measurements and submitted a questionnaire to 20 users to assess the user-friendliness of each test. RESULTS: All D-dimer tests showed negative predictive values higher than 98%. Sensitivity was high for all point-of-care tests, with a range of 0.91 (Clearview Simplify) to 0.99 (Vidas). Specificity varied between 0.39 (Pathfast) and 0.64 (Clearview Simplify). The quantitative point-of-care tests showed similar and high discriminative power for DVT, according to cal- culated areas under the ROC curves (range 0.88 – 0.89). The quantitative Vidas and Pathfast devices showed limited user-friendliness for primary care, owing to a laborious calibration process and long analyzer warm-up time compared to the Cardiac and Triage. For the qualitative Clearview Simplify assay, no ana- lyzer or calibration was needed, but interpretation of a test result was sometimes difficult because of poor color contrast. CONCLUSIONS: Point-of-care D-dimer assays show good and similar diagnostic accuracy. The quantitative Car- diac and Triage and the qualitative Clearview Simplify D-dimer seem most user-friendly for excluding DVT in the doctor’s office. © 2010 American Association for Clinical Chemistry More than 75% of the patients in whom deep vein thrombosis (DVT) 3 is suspected and who are referred for objective testing— commonly performed with leg- compression ultrasonography– do not have DVT (1, 2 ). D-dimer testing for DVT has been introduced to improve the diagnostic process and, in particular, to reduce the number of unnecessary referrals for leg-compression ultrasonography. Concentrations of D-dimer are increased in patients with DVT, but may also be increased in other conditions such as cancer, infections, pregnancy, and recent surgery. Hence, D-dimer tests are typically used as rule-out tests (3, 4 ). Although D-dimer testing is readily available to many hospital physicians within their central laboratories, this is often not the case for primary care physicians. Most patients with suspected DVT, however, are first seen in primary care settings, and for such cases referral to central laboratories for D-dimer testing is not always a practical solution. Therefore, to enable exclusion of DVT in the doctor’s office, several point-of-care D-dimer tests have been developed (5–14 ). These tests yield results within 10 –15 min and in many cases may eliminate the need for referrals to central laboratories or diagnostic services. Indeed, a recent study demon- strated that the use of a qualitative point-of-care D-dimer test was both safe and cost-effective in pri- mary care (15, 16 ). Consequently, the introduction of point-of-care D-dimer tests for use in primary care set- tings is eagerly awaited. As with all new therapies, however, diagnostic devices, including biomarker tests, must undergo 1 Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands; 2 Department for Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, the Netherlands. * Address correspondence to this author at: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, the Netherlands, P.O. Box 85500, 3508 GA Utrecht, the Netherlands. Fax +31-88-75-68-099; e-mail K.G.M.Moons@umcutrecht.nl. Received April 1, 2010; accepted August 16, 2010. Previously published online at DOI: 10.1373/clinchem.2010.147892 3 Nonstandard abbreviations: DVT, deep vein thrombosis; D-DU, D-dimer units; FEU, fibrinogen equivalent units; AUC, area under the ROC curve. Clinical Chemistry 56:11 1758–1766 (2010) Point-of-Care Testing 1758