Optimizing selection of in vitro tests for diagnosing thyroid disorders.

The optimal utilization of the thyroid related radioimmunoassays T3, T4, and TSH-RIA is derived from analysing the clinical and laboratory data for 974 patients with functional thyroid disorders. A statistical computer analysis of the contribution of each of the three tests, and in combination, to the final diagnoses of hypothyroid, euthyroid, and hyper thyroid states was designed. The best contributing test for hypothyroidism and euthyroidism was TSH-RIA (98.5 and 93%, respectively). T4/T3 + TSH-RIAs were the optimal dual combination for diagnosing euthyroidism (98.0%). For diagnosing hyperthyroidism T4-RIA was the best single test (82.5%) followed by T3 + T4 as an optimal dual combination (95%). Using all three tests was of no significant additional value over dual combinations. It is concluded that the work and cost of randomly performing three tests routinely is not justified without clinical basis. An algorithm is proposed to guide thyroid studies based on computer analyses of the above-mentioned single or dual-test combinations to establish accurate diagnosis at the lowest laboratory cost.

Preoperative parathyroid localization by superimposed iodine-131 toluidine blue and technetium-99m pertechnetate imaging.

A new parathyroid scintigraphic localization study by a dual radioisotope technique using radioiodinated toluidine blue (RTB) for the parathyroids and 99mTc for thyroid imaging is presented. A simple RTB labeling procedure achieving 99% tagging of the 131I-TB was used. The RTB was found to be a highly specific parathyroid radiotracer, consequently enabling superimposition of the delineated thyroid gland over the RTB avid parathyroid foci without a need for subtraction of the thyroid or vascular background. Forty-six patients with primary hyperparathyroidism underwent scintigraphic study prior to cervical (41 patients) or mediastinal (5 patients) exploration and 67 pathological parathyroid glands (34 adenomas and 33 hyperplasias) were excised. On follow-up, serum calcium level returned to normal in all patients. Correlation of the scintigraphic results with the surgical findings disclosed a sensitivity of 93%, with a specificity of 80% and an overall accuracy of 87%. This new simplified and specific RTB scintigraphic method justifies its use as a routine procedure for preoperative parathyroid scintigraphic localization in primary hyperparathyroidism.

Blood-C.S.F. barriers dysfunction in the chronic organic brain syndrome; a R.I.A. study.

C.S.F. samples of 35 patients, who suffered from verified chronic, non-tumorous organic brain syndrome, were radioimmunoassayed for T4 and T.S.H., and were compared to C.S.F.-R.I.A. samples from a control group of patients who underwent myelography because of lumbar disc. In addition T4 and T.S.H. plasma levels were evaluated in the O.B.S. patients. C.S.F. T4 and T.S.H. levels were significantly higher in 65% of the O.B.S. group of patients than those of the control group. The average determinations for T4 were: 0.77 muh/100 ml in O.B.S. group as against 0--0.4 micrograms/100 ml in the C.S.F.'s of the control group. P greater than 0,001 T.S.H. C.S.F. levels were 1.33 microU/ml in the O.B.S. group, and 0--0.6 microU/ml in the control group (P greater than 0.005). It is suggested that the elevated R.I.A. values of these hormones in the C.S.F. of the O.B.S. patients reflect a disruption of blood-C.S.F. barriers. Therefore in the organic brain syndrome there seems to exist a pathophysiological dysfunction of brain barriers in addition of the neural damage.

Triiodothyronine radioimmunoassay and its application to thyroid disorders.

An accurate, highly sensitive triiodothyrone (T3) radioimmunoassay system is described. Direct measurement in serum is made possible by the use of T3-free serum for standards, and blocking of T3 binding to thyroxine (T4)-binding globulin with salicylate. T4 cross reactivity was less than 0.3%. Mean T3 levels in 55 euthyroid, 32 hyperthyroid and 19 primary hypothyroid patients were 1.46 +/- 0.17, 5.34 +/- 1.86 and 0.49 +/- 0.34 (SD) ng/ml, respectively. T3 was found to be a more sensitive index than T4 in hyperthyroidism; in hypothyroidism it overlapped with euthyroidism. The presence of goiter had no effect on T3 concentrations in euthyroid patients. Among the patients studied, eight were found to have T3 toxicosis, including two patients with recurrent thyrotoxicosis. A significant T3 elevation was also found in euthyroid patients after thyroidectomy whereas T4 remained normal. The extent of T4 and T3 elevation was similar during the initial phase of subacute thyroiditis. There were significantly lower T3 values and higher thyroid-stimulating hormone values in umbilical cord blood than in maternal blood. In two euthyroid subjects, thyrotropin-releasing hormone stimulation caused a 50% rise in T3 levels and no change in T4 levels over a 2-h period.