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Diagnostic evaluation of the adrenal incidentaloma: decision and cost-effectiveness analyses
B A Dwamena1, R T Kloos, A M Fendrick
1Department of Internal Medicine, School of Public Health, The University of Michigan, and Department of Veteran Affairs Medical Centers, Ann Arbor 48105, USA.
Unlabelled:
The goal of this study was to examine the clinical and economic outcomes of alternative diagnostic strategies for differentiating benign from malignant adrenal masses.
Methods:
We used cost-effectiveness assessment derived from decision analysis and the economic perspective of the payer of health care services. One-time evaluation with fine-needle aspiration (FNA) and combinations of chemical-shift MRI, noncontrast CT, 131I-6beta-iodomethylnorcholesterol (NP-59) scintigraphy, with or without FNA, in a hypothetical cohort of 1000 patients with incidentally discovered unilateral, nonhypersecretory adrenal masses. We calculated and compared the diagnostic effectiveness, costs and cost-effectiveness of the alternative strategies based on estimates from published literature and institutional charge data.
Results:
At an assumed baseline malignancy rate of 0.25, diagnostic utility varied from 0.31 (CT0) to 0.965 (NP-59) and diagnostic accuracy from 0.655 [noncontrast CT using a cut-off attenuation value of > or = 0 (CT0)] to 0.983 (NP-59). The average cost per patient per strategy ranged from $746 (NP-59) to $1745 (MRI +/- FNA). The best and worst potential cost-to-diagnostic utility ratios were 773 (NP-59) and 2839 (CT0) and 759 (NP-59) and 1982 (MRI +/- FNA) for cost and diagnostic accuracy, respectively. The NP-59 strategy was the optimal choice regardless of the expected outcome examined: cost, diagnostic utility, diagnostic accuracy or cost-effectiveness. Varying the prevalence of malignancy did not alter the cost-effectiveness advantage of NP-59 over the other diagnostic modalities.
Conclusion:
Based on available estimates of reimbursement costs and diagnostic test performance and using reasonable clinical assumptions, our results indicate that the NP-59 strategy is the most cost-effective diagnostic tool for evaluating adrenal incidentalomas over a wide range of malignancy rates and that additional clinical studies are warranted to confirm this cost-effectiveness advantage.