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March 1989

Sensitivity, Specificity, and Cost-effectiveness of the Sensitive Thyrotropin Assay in the Diagnosis of Thyroid Disease in Ambulatory Patients

Author Affiliations

From the Departments of Internal Medicine–Endocrinology and Metabolism (Dr de los Santos) and Internal Medicine and Physiology (Dr Mazzaferri), Ohio State University, Columbus; and Department of Medicine and Physiology, University of Nevada School of Medicine, Reno (Dr Starich).

Arch Intern Med. 1989;149(3):526-532. doi:10.1001/archinte.1989.00390030032006

• The sensitivity and specificity of two sensitive thyrotropin assays were compared with those of other standard thyroid function tests in 544 ambulatory subjects who were clinically euthyroid, thyrotoxic, or hypothyroid. Both sensitive thyrotropin assays had the highest sensitivity and specificity (95%/89% and 92%/95%), followed by estimated free thyroxine (T4) level (82% and 94%), calculated free T4 index (78% and 93%), and free triiodothyronine index (86% and 88%). Sensitivity of the two thyrotropin assay kits in the diagnosis of thyrotoxicosis was 86% and 95%, and that in the diagnosis of hypothyroidism was 92% and 94%. Other tests were nearly as sensitive in the diagnosis of thyrotoxicosis but not hypothyroidism. A cost analysis of a testing strategy that used either total T4, free T4 index, or sensitive thyrotropin assay alone as the first-line thyroid test disclosed that to establish the patient's thyroid metabolic status would have cost $11 093, $14 536, and $24 902, respectively, using each test first. We suggest that, at current prices, routine use of the thyrotropin assay as a first-line test in ambulatory patients is not as cost-effective as the free T1 index.

(Arch Intern Med 1989;149:526-532)

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