Value of quantitative D-dimer assays in identifying pulmonary embolism: implications from a sequential decision model.
OBJECTIVE
To examine the cost-effectiveness of a quantitative D-dimer assay for the evaluation of patients with suspected pulmonary embolism (PE) in an urban emergency department (ED).


METHODS
The authors analyzed different diagnostic strategies over pretest risk categories on the basis of Wells criteria by using the performance profile of the ELISA D-dimer assay (over five cutoff values) and imaging strategies used in the ED for PE: compression ultrasound (CUS), ventilation-perfusion (VQ) scan (over three cutoff values), CUS with VQ (over three cutoff values), computed tomography (CT) angiogram (CTA) with pulmonary portion (CTP) and lower-extremity venous portion, and CUS with CTP. Data used in the analysis were based on literature review. Incremental costs and quality-adjusted-life-years were the outcomes measured.


RESULTS
Computed tomography angiogram with pulmonary portion and lower-extremity venous portion without D-dimer was the preferred strategy. CUS-VQ scanning always was dominated by CT-based strategies. When CTA was infeasible, the dominant strategy was D-dimer with CUS-VQ in moderate- and high-Wells patients and was D-dimer with CUS for low-Wells patients. When CTP specificity falls below 80%, or if its overall performance is markedly degraded, preferred strategies include D-dimer testing. Sensitivity analyses suggest that pessimistic assessments of CTP accuracy alter the results only at extremes of parameter settings.


CONCLUSIONS
In patients in whom PE is suspected, when CTA is available, even the most sensitive quantitative D-dimer assay is not likely to be cost-effective. When CTA is not available or if its performance is markedly degraded, use of the D-dimer assay has value in combination with CUS and a pulmonary imaging study. These conclusions may not hold for the larger domain of patients presenting to the ED with chest pain or shortness of breath in whom PE is one of many competing diagnoses.
Duriseti
Ram S
RS
Department of Veterans Affairs Palo Alto Health Care System, CA 94304, USA. ram1@stanford.edu
Shachter
Ross D
RD
Brandeau
Margaret L
ML
D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D003951:Diagnostic Errors / Q000191:economics; D004635:Emergency Medicine / Q000295:instrumentation; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis* / Q000191:economics*; D006801:Humans; D011655:Pulmonary Embolism / Q000097:blood* / Q000175:diagnosis*; D019057:Quality-Adjusted Life Years; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D