Detecting Unsuspected Thyroid Dysfunction by the Free Thyroxine Index

• The free thyroxine index (FTI) was used in 2,704 adults to detect unsuspected thyroid dysfunction. Among 2,581 adults found to be clinically euthyroid without thyroid medication, 2,571 had a truly normal FTI (121 to 360) and ten had a falsely abnormal FTI (seven 360). Among 25 subjects with newly diagnosed thyroid dysfunction, there were eight hyperthyroid (prevalence, 0.31%) and 14 hypothyroid (prevalence, 0.50%) subjects. The sensitivity of the FTI was 1.0, and the specificity was 0.996. The predictive value of an abnormal FTI with a prevalence of 0.81% was 67%. The cost to find a new case averaged $127. The annual incidence of symptomatic hyperthyroidism was 0.05%; of hypothyroidism, about 0.08%. We conclude that the FTI is cost-effective for case finding in thyroid dysfunction. (Arch Intern Med 140:1045-1049, 1980)

[1]  D. Solomon,et al.  Misleadingly low free thyroxine index and usefulness of reverse triiodothyronine measurement in nonthyroidal illnesses. , 1979, Annals of internal medicine.

[2]  E. Cooper,et al.  Thyroid hormones in the elderly sick: "T4 euthyroidism". , 1975, British medical journal.

[3]  D. Appleton,et al.  THE SPECTRUM OF THYROID DISEASE IN A COMMUNITY: THE WHICKHAM SURVEY , 1977, Clinical endocrinology.

[4]  M. Birkhäuser,et al.  DIAGNOSIS OF HYPERTHYROIDISM WHEN SERUM-THYROXINE ALONE IS RAISED , 1977, The Lancet.

[5]  D. Barker,et al.  Computer-based screening system for patients at risk of hypothyroidism. , 1969, Lancet.

[6]  W. E. Cobb,et al.  Why does anyone still use desiccated thyroid USP? , 1978, The American journal of medicine.

[7]  J. Wolfe,et al.  Breast cancer. Relationship to thyroid supplements for hypothyroidism. , 1976, JAMA.

[8]  S G Pauker,et al.  The diagnostic importance of the normal finding. , 1978, The New England journal of medicine.

[9]  M. Collen,et al.  Cost analyses of alternative health examination modes. , 1977, Archives of Internal Medicine.

[10]  L. Braverman,et al.  Adverse effects of iodides on thyroid function. , 1975, The Medical clinics of North America.

[11]  J. Hershman.  Clinical Application of Thyrotropin-Releasing Hormone , 1974 .

[12]  S R Garfield,et al.  The delivery of medical care. , 1970, Scientific American.

[13]  E. Keeler,et al.  Primer on certain elements of medical decision making. , 1975, The New England journal of medicine.

[14]  R. Utiger,et al.  Thyroidal and peripheral production of thyroid hormones. Review of recent findings and their clinical implications. , 1977, Annals of internal medicine.

[15]  D. Evered,et al.  Grades of Hypothyroidism , 1973, British medical journal.

[16]  R. Wallace,et al.  Thyroid hormone use in patients with breast cancer. Absence of an association. , 1978, JAMA.

[17]  H. Meinhold,et al.  Evidence of lower toxicity during thyroxine suppression after a single 3-mg L-thyroxine dose: comparison to the classical L-triiodothyronine test for thyroid suppressibility. , 1974, The Journal of clinical endocrinology and metabolism.

[18]  Arthur F. Krieg,et al.  Why are clinical laboratory tests performed? When are they valid? , 1975, JAMA.

[19]  J. Hershman,et al.  A sensitive and precise radioimmunoassay for human thyroid-stimulating hormone. , 1975, The Journal of clinical endocrinology and metabolism.

[20]  K. Levin,et al.  Studies on subclinical hypothyroidism with special reference to the serum lipid pattern. , 2009, Acta medica Scandinavica.

[21]  S. Shalet,et al.  VALUE OF ROUTINE SERUM-TRIIODOTHYRONINE ESTIMATION IN DIAGNOSIS OF THYROTOXICOSIS , 1975, The Lancet.

[22]  S. Refetoff,et al.  Study of four new kindreds with inherited thyroxine-binding globulin abnormalities. Possible mutations of a single gene locus. , 1972, The Journal of clinical investigation.

[23]  L. Elveback,et al.  Epidemiologic aspects of Hashimoto's thyroiditis and Graves' disease in Rochester, Minnesota (1935-1967), with special reference to temporal trends. , 1972, Metabolism: clinical and experimental.

[24]  L. Elveback,et al.  Graves' disease in Olmsted County, Minnesota, 1935 through 1967. , 1970, Mayo Clinic proceedings.

[25]  P. Woolf.  Painless thyroiditis as a cause of hyperthyroidism: subacute or chronic lymphocytic? , 1978, Archives of internal medicine.

[26]  A. H. Reed,et al.  Influence of statistical method used on the resulting estimate of normal range. , 1971, Clinical chemistry.

[27]  M. Surks,et al.  High incidence of decreased serum triiodothyronine concentration in patients with nonthyroidal disease. , 1975, The Journal of clinical endocrinology and metabolism.

[28]  D. Baldwin,et al.  Incidence of thyroid disorders in Connecticut. , 1978, JAMA.