Prospective Study of the Diagnostic Accuracy of the Simplify D-dimer Assay for Pulmonary Embolism in Emergency Department Patients
The ideal screening strategy to exclude pulmonary embolism (PE) in the emergency department (ED) setting would be, fast, cheap, accurate, and easy to use. The d-dimer assay (Simplify D-dimer; Agen Biomedical; Brisbane, Australia) is a single-use, individually packaged immunofiltration cartridge assay. The kits and the reagents can be stored at room temperature. The user adds a drop of whole blood to a well, followed by a few drops of buffer. The test result is read in 10 min at the bedside. The test has an acquisition cost of < $20. However, to ensure patient safety and to maintain a defensible standard of care, any PE screening strategy must have sufficiently high sensitivity and specificity to reliably produce a posttest probability < 1.0%. add comment
Very few published studies have addressed the sensitivity and specificity of the Simplify D-dimer assay for the diagnosis of PE. Researchers2’ remain concerned that qualitative d-dimer assays may demonstrate lower diagnostic sensitivity compared with quantitative d-dimer assays, which are becoming more widely used in EDs to rule out the diagnosis of PE. In the present report, we test the hypothesis that the Simplify D-dimer assay can produce a posttest probability of PE < 1.0% in certain low-risk, symptomatic ED patients. The specific aims were as follows: (1) to report the clinical characteristics of ED patients tested with the Simplify D-dimer assay; (2) to measure the diagnostic sensitivity, specificity, and negative likelihood ratio for the d-dimer assay, and examine the posttest probability of PE in low risk-patients with a negative d-dimer result; and (3) to test if spectrum bias affected the diagnostic indexes. This protocol was approved by the Carolinas Medical Center Institutional Review Board. Carolinas Medical Center is an urban teaching hospital with a residency in emergency medicine and a 2002 census of 107,000. Research participants were ED patients of all ages who were selected by a board-certified emergency physician to undergo a structured PE rule-out protocol, using methods we have described previously.