Comparison of five point‐of‐care D‐dimer assays with the standard laboratory method

Abstract

D-dimer (DD) assays are effective for the exclusion of deep-vein thrombosis (DVT), but point-of-care (POC) DD assays have not been fully evaluated. We have compared five POC DD assays (Pathfast, Cardiac, Vidas, Stratus and NycoCard) with our routine DD method (Tinaquant), testing 60 samples from patients with suspected DVT. Using 0.5 μg/mL as a cut-off value, four samples tested negative with Tinaquant were positive with Pathfast. There were no Tinaquant-positive samples tested negative with Pathfast, while the overall agreement (k = 0.81) was very good. Four samples were discrepant between Tinaquant and Cardiac (cut-off, 0.4 μg/mL), while k = 0.72. One of two Tinaquant-negative samples was shown to be positive for either Vidas (cut-off, 0.5 μg/mL) or Stratus (cut-off, 0.4 μg/mL), respectively. The agreement with Tinaquant was excellent for both Vidas (k = 0.92) and Stratus (k = 0.94). Total CV was <10% for all four assays. Eight samples (of 27) were negative with NycoCard although they were positive with Tinaquant, while CV was 41%. Vidas cannot be considered a POC assay because the sample has to be centrifuged before testing. Our findings have also shown that the use of NycoCard is inappropriate. Stratus and Pathfast have a similar analytical profile in comparison with the Tinaquant method. Cardiac is potentially less sensitive but may still be acceptable for use. It seems that the employment of these three assays for rapid bed-side analysis offers a possibility to adequately rule out DVT in outpatients within minutes after admission.