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

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

J Postgrad Med. 2011 Apr-Jun;57(2):109-14

Authors: Bayes HK, O'Dowd CA, Glassford NJ, McKay A, Davidson S

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<0.0001). The positive diagnostic yield for PTE on CT pulmonary angiogram (CTPA) increased significantly from 10% in period 1 to 23% in period 2 (P=0.039). Conclusion : D-dimers must be used judiciously in the assessment of suspected PTE. Appropriate use of D-dimers can provide many benefits, including reductions in diagnostic imaging (and thus radiation exposure), admission rates, and length of inpatient stay.

PMID: 21654131 [PubMed - in process]

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