D-dimer assays - A help or hindrance in suspected pulmonary thromboembolism assessment?

Background : Suspected pulmonary thromboembolism (PTE) is a common presentation to acute medical units and can cause diagnostic difficulty. National guidelines on PTE management highlight the need for clinical probability assessment and D-dimer assays to ensure appropriate use of diagnostic imaging. D-dimers are used widely in UK hospitals, yet concern exists regarding their misuse. Aims : In this study we aimed to assess the impact of the introduction of D-dimer assays, combined with clinical probability assessment, for evaluation of suspected PTE in our unit. Materials and Methods : This was a prospective audit of all patients presenting with suspected PTE over two 12-week periods, exactly 1 year apart. D-dimers were introduced into our unit between these two periods. We recorded the clinical probability score, potential causes of false-positive D-dimer assay, diagnostic imaging result, patient outcome, admission rates, and length of inpatient stay. Statistical Analysis : Categorical variables were compared using a 2 x 2 chi-square test or Fisher′s exact test. Groups were compared utilizing the two-sample t-test or Mann-Whitney U test. Results : A total of 190 patients were included in the study; 65% were female. PTE was confirmed in 8.4%. Patients in both audit periods were comparable with regard to suitability for D-dimer measurement. Following D-dimer introduction, 40 out of 110 patients in period 2 could be discharged directly from the emergency department. Of those admitted to hospital, the median length of stay was significantly reduced in period 2 (3 days in period 1 vs 1 day in period 2; P=0.0007). Use of diagnostic imaging was significantly reduced following the introduction of D-dimers (90% in period 1 vs 40% in period 2; P