An Audit on D-dimer Use in the Assessment of Patients with Suspected Acute Pulmonary Embolism

Abstract number: P2234

Yong T, Hedger S, Gallus A, Coghlan D

The D-dimer assay is increasingly used to exclude clinically suspected pulmonary embolism (PE) in patients with a low clinical pre-test probability (PTP) of PE, but its utility in an uncontrolled clinical setting is unknown. This study compares D-dimer testing in a tertiary referral hospital with recommended usage. We retrospectively reviewed D-Dimer requests during a three-month period for 211 presentations with clinically suspected PE (8 confirmed) in 196 patients. D-dimer was measured before any imaging procedure, using the Tinaquant immunoturbidimetric assay (Roche, on a Hitachi 911; >500 ng/L was considered a positive test result). PTP was retrospectively derived from case-notes (Wells scores in 211 presentations and Geneva scores in 101; the higher score was applied). D-dimer requests were related to PTP (138 low, 71 intermediate, 2 high) and utility of D-dimer results was derived from the subsequent diagnostic work-up. The D-Dimer assay request was deemed appropriate in the 138 presentations (65%) with a low PTP. 26 of 94 presentations (28%) were further investigated despite a low PTP and negative D-dimer test result, with one case of PE identified. Regardless of PTP, 49/87 presentations (56%) with a positive D-dimer test result were not investigated further. In the intermediate PTP group with a positive D-dimer result, 22/43 presentations (51%) did not have imaging tests. Our findings indicate that D-dimer use in this hospital complies poorly with current evidence-based practice. Although 72% of presentations with a low PTP for PE and a negative D-Dimer test were not further investigated, only 39% and 49% of those with a low or intermediate PTP respectively and positive D-Dimer result had imaging for PE. Indiscriminate D-dimer testing without an impact on imaging patterns is wasteful and potentially leads to missed diagnoses. Testing guidelines in the Emergency Department have been introduced since this audit, which will be repeated to measure their impact on clinical practice.