Comparison of high specificity with standard versions of a quantitative latex D-dimer test in the assessment of community pulmonary embolism HaemosIL D-dimer HS and Pulmonary Embolism

Background: D-dimer assays are sensitive but have poor specificity. False positive results lead to extra imaging and hospital admissions. Objectives: To make a pilot comparison of the diagnostic accuracy of the standard quantitative latex HemosIL D-dimer assay with a newer HemosIL D-dimer HS version designed to have improved specificity. Patients/Methods: Consecutive patients presenting from the community to an Emergency Department that were investigated for suspected pulmonary embolism using a D-dimer test were included in the study. Standard and D-dimer HS tests were performed. Pulmonary Embolism was diagnosed on the basis of imaging studies or post-mortem at any time from presentation to 90 days thereafter. Results: The prevalence of Pulmonary Embolism was 4.5% (18/402). The sensitivity, specificity, negative predictive value, and positive predictive value for the standard quantitative D-dimer test was 100% (81.5-100.0), 49.2% (44.1-54.3), 100% (98.1-100.0), and 8.5% (5.1-13.0), respectively, and 100%. (81.5-100.0). 58.3% (53.2-63.3), 100% (98.4-100.0), and 10.1% (6.1-15.5), for the D-dimer HS test. There were 35 (16%) fewer 'false positives' using the D-dimer HS assay compared with the standard assay. Conclusions: D-dimer HS has superior specificity to the standard quantitative D-dimer test without any loss of sensitivity. The generation of fewer false positive results should lead to less unnecessary diagnostic imaging; the use of which is associated with increased hospital admissions and length of stay. The HS assay may therefore have significant health economic benefits. (C) 2008 Elsevier Ltd. All rights reserved.