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Cost-effective diagnostic strategies in patients with a high, intermediate, or low clinical probability of pulmonary embolism |
Lee JA, Zierler BK, Liu CF, Chapko MK |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary This study examined the cost-effectiveness of strategies, including rapid quantitative D-dimer assays, lower extremity venous duplex ultrasound, ventilation and perfusion scans, and multislice computed tomography (CT) angiography, to diagnose pulmonary embolism in patients with a high, intermediate, or low probability of embolism. The authors concluded that D-dimer assays then CT had the lowest cost per life saved for all patients. The cost-effectiveness framework was conventional and the results were clearly reported. The conclusions seem robust. Type of economic evaluation Cost-effectiveness analysis Study objective This study examined the cost-effectiveness of strategies to diagnose pulmonary embolism in patients with a high, intermediate, or low probability of having it. Interventions Nine strategies were examined, including sequences of rapid quantitative D-dimer assays (enzyme-linked immunosorbent assay; ELISA), lower extremity venous duplex ultrasound, ventilation and perfusion scans, and multislice computed tomography (CT) angiography. In sequential strategies, the second or third strategy depended on the results of the previous one. Patients with a high probability of pulmonary embolism received treatment, while those with a negative result underwent the next strategy. The nine strategies were ventilation and perfusion then pulmonary angiography; ventilation and perfusion then CT; CT; CT then ultrasound; ultrasound then CT; D-dimer assays then CT; D-dimer assays then ultrasound then CT; D-dimer assays then CT then ultrasound; and D-dimer assays then ventilation and perfusion then pulmonary angiography. Location/setting USA/secondary and tertiary care. Methods Analytical approach:The analysis was based on a decision tree, with a three-month time horizon. The authors stated that the perspective of the third-party payer was adopted. Effectiveness data:The clinical inputs were from various published studies. The pulmonary embolism prevalence and some accuracy data were from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED II) study. Three levels of pulmonary embolism prevalence (low, intermediate, and high) were analysed. The accuracy (sensitivity and specificity) of each diagnostic strategy was the key input for the model. Monetary benefit and utility valuations:Not considered. Measure of benefit:The three-month probability of survival was the summary benefit measure. Cost data:The economic analysis included the costs of diagnostic tests, anticoagulation therapy and contrast-induced acute renal failure requiring haemodialysis. Most of the costs were from the Centers for Medicare and Medicaid Services, while the other costs were from published sources. All costs were in US $ and the price year was 2006. Analysis of uncertainty:One-way sensitivity analyses were carried out to investigate how robust the model results were to variations in all the inputs, using wide ranges of clinically relevant values. Results Dominated strategies, which were more expensive and less effective than another option, were excluded. In patients with a high probability of pulmonary embolism, the expected costs were $4,893 with D-dimer assays then CT, $5,304 with D-dimer assays then ultrasound then CT, and $5,610 with ultrasound then CT. The probability of survival was 89.04% with D-dimer then CT, 89.61% with D-dimer then ultrasound then CT, and 89.85% with ultrasound then CT. The incremental cost per additional life saved was $72,446 with D-dimer assays then ultrasound then CT, and $124,815 with ultrasound then CT, compared with D-dimer then CT. In patients with an intermediate clinical probability, the incremental cost per additional life saved was $110,933 with D-dimer assays then ultrasound then CT, and $300,377 with ultrasound then CT, compared with D-dimer then CT. In patients with a low clinical probability, the incremental cost per additional life saved was $507,658 with CT, and $4,064,823 with ultrasound then CT, compared with D-dimer then CT. D-dimer assays then CT was the most cost-effective strategy in patients with all three clinical probabilities of pulmonary embolism. These findings were robust to most variations in the model inputs. For patients with low probability, when the specificity of CT was lower than 95%, the strategy of D-dimer assays then ventilation and perfusion then pulmonary angiography was economically attractive. When the sensitivity of ultrasound was less than 34%, ultrasound then CT was dominated for patients with low probability, and for patients with intermediate or high probability, the strategy of D-dimer assays then CT then ultrasound became dominant instead of D-dimer then ultrasound then CT. Authors' conclusions The authors concluded that a diagnostic strategy of D-dimer assays then CT had the lowest cost per life saved in all patients with suspected pulmonary embolism. CRD commentary Interventions:The analysis considered a wide range of diagnostic strategies that reflected the options for patients with suspected pulmonary embolism. A description of each diagnostic procedure was given. Effectiveness/benefits:Little information was given on the sources for the clinical inputs. Test accuracy appears to have been from recent diagnostic studies, which were not described, making it difficult to judge their validity. Sensitivity analysis was conducted on the sensitivity and specificity of each test and with different scenarios of pulmonary embolism prevalence. Avoided deaths due to pulmonary embolism was the main outcome of the analysis, but QALYs would have been a more appropriate benefit measure. Costs:The economic analysis was restricted to the viewpoint of the health service provider and only the direct medical costs were included. The unit costs of diagnostic procedures were reported, while other costs were presented as category totals and were from published studies, which were likely to be representative of the US context. Typical US sources were used for the diagnostic test costs. Variations in cost inputs were considered in the sensitivity analyses. Reflation exercises are possible, as the price year was explicitly reported. Analysis and results:Only the results for non-dominated strategies were reported, but all findings were presented graphically. The results were given for each of the three categories of clinical probability of pulmonary embolism. An incremental approach was appropriately used to synthesise the costs and benefits of the strategies. The uncertainty was investigated, using a deterministic approach, that focused on variations in individual inputs. A more comprehensive and simultaneous approach would have been informative. The authors compared their results with those of other published studies and they highlighted the fact that this analysis used more recent accuracy data. The findings appear to be specific to the USA and might not be transferable to other settings. Concluding remarks:The cost-effectiveness framework was conventional and the results were clearly reported. The authors’ conclusions appear to be robust. Funding Support received from the Agency for Healthcare Research and Quality, USA. Bibliographic details Lee JA, Zierler BK, Liu CF, Chapko MK. Cost-effective diagnostic strategies in patients with a high, intermediate, or low clinical probability of pulmonary embolism. Vascular and Endovascular Surgery 2011; 45(2): 113-121 Indexing Status Subject indexing assigned by NLM MeSH Anticoagulants /economics /therapeutic use; Biomarkers /blood; Blood Chemical Analysis /economics; Cost-Benefit Analysis; Decision Support Techniques; Decision Trees; Drug Costs; Fibrin Fibrinogen Degradation Products /analysis; Health Care Costs; Humans; Models, Economic; Patient Selection; Perfusion Imaging /economics; Predictive Value of Tests; Pulmonary Embolism /diagnosis /drug therapy /economics /etiology /mortality; Risk Assessment; Risk Factors; Survival Analysis; Survival Rate; Time Factors; Tomography, X-Ray Computed /economics; Treatment Outcome; Ultrasonography, Doppler, Duplex /economics AccessionNumber 22011000841 Date bibliographic record published 06/07/2011 Date abstract record published 19/11/2012 |
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