Routine calcitonin measurement in management of thyroid nodules: A decision analysis approach
Background: Calcitonin is a reliable marker for medullary thyroid carcinoma (MTC) and is useful in follow-up of patients with MTC. While fine needle aspiration biopsy (FNA) is very sensitive and specific for differentiated thyroid carcinoma (follicular and papillary lesions), it is less reliable for diagnosis of MTC. It has been proposed that calcitonin should be used in assessment of patients with thyroid nodules. We have calculated the costs of this strategy.
Methods: We used published data concerning the prevalence of MTC in thyroid nodular disease (5 %), the sensitivity and specificity of calcitonin measurement (100% and 96%) and FNA (50% and 95%) in the diagnosis of medullary thyroid carcinoma, the 10-year survival of patients diagnosed early (97%) compared with those diagnosed late (70%). Calcitonin measurement currently costs our laboratory £35. We assumed that a single (unstimulated) assay was performed on patients with a negative FNA result. Using representative costs of extra medical resources incurred because of late diagnosis allows calculation of the likely cost per life saved. A sensitivity analysis was performed to determine the effect of changes in these values on the resultant costs. Using a decision tree analysis, we calculated the cost per calcitonin measurement and cost per life at which routine calcitonin measurement becomes cost saving.
Results: The cost of calcitonin assays per extra tumour identified was approximately £8600, resulting in a cost per life saved of approximately £32,000. In the decision tree analysis, routine calcitonin measurement was cost saving at a cost per life of approximately £110,000, with a cost per quality adjusted life year of less than £5000.
Conclusion: Routine measurement of calcitonin in patients with thyroid nodules and a negative FNA is cost effective, and is likely to be more cost effective as assay costs fall.