The Measurement of Human Chorionic Gonadotropin for Pregnancy Testing

/Among many measurable hormones, human chorionic gonadotropin (FICG) is commonly used for pregnancy testing because it is very sensitive and relatively specific. Pregnancy can be identified shortly after implantation. Because some reagents cross-react with luteinizing hormone (LH), the sensitivity of urine tests has been adjusted to maintain specificity. Radioreceptor assay s on serum are more sensitive than urine tests but similarly lack specificity. The problems of LH cross-reactivity are eliminated by antisera specific for the beta subunit. Quantitation of HCG provides additional information useful in diagnosing ectopic pregnancy, providing a prognosis in threatened abortion, and following neoplasms. Considerations of cost, availability, accuracy, and sensitivity determine which test should be selected

A Thyroid Testing Algorithm: Results of a Pilot Study

We conducted a pilot study to evaluate an algorithm for thyroid function testing consisting of initial serum thyrotropin values, measured by a sensitive immunoradiometric assay (TSH-IRMA) followed by a computer-directed decision to order further studies. We divided 216 outpatients according to their serum TSH-IRMA values as follows: suppressed (\u3c 0.1 mU/L, group I); low (0.1 to 0.4 mU/L, group II); normal (0.5 to 5.0 mU/L, group III); and high (\u3e 5.0 mU/L, group IV). Thyroxine (T4), resin uptake (RU). and free thyroxine index (FTI) tests on groups I, Il, and IV revealed that T4 and RU were normal for most patients in all groups and FTI was normal in 80% of group 1, 93.4 % of group ll, and 93.3% of group IV. All patients in group I were designated hyperthyroid from either an exogenous or endogenous source. All patients in group ll were clinically euthyroid except one; 50% were taking either L-thyroxine or propylthiouracil and 50% had no identifiable thyroid disease. Patients in group IV were hypothyroid. Overall, TSH was more effective in detecting both hypothyroidism and hyperthyroidism than either serum T4, RU ratio, or both combined in FTI since results of these measures fell in the normal range for most patients in all groups. We conclude that a computer-directed algorithm with TSH-IRMA as the initial step is useful in the evaluation of suspected thyroid dysfunction, that T4 and RU may be helpful when TSH is abnormal or borderline, and that suppressed TSH-IRMA values (\u3c0.1 mU/L) but not low values (0.1 to 0.4 mU/L) are consistently associated with hyperthyroidism. Results obtained by use of the algorithm may be misleading in patients with hypothalamic pituitary dysfunction, but its use should reduce the number of redundant and unnecessary T4 and RU tests

Contemporary Approach to Thyroid Disease Emphasizing Use of High-Sensitivity Thyrotropin Assays

Capabilities of new high-sensitivity immunoradiometric assays for thyroid-stimulating hormone (TSH-IRMA) to distinguish among hypothyroid, euthyroid, and hyperthyroid subjects and patient groups with low TSH for nonthyroidal causes suggested an algorithmic approach (directed TSH) to the evaluation of patients with suspected thyroid disease. Utilizing the algorithm, a TSH-IRMA result outside normal limits (0.5 to 5.0 mUlL) generates follow-up tests on the same sample. The interpretation of thyroid function tests (TSH-IRMA, thyroxine, resin uptake, free thyroxine index) and associated studies in the context of different clinical settings is reviewed. The approach is a cost-effective and efficient utilization of laboratory services

Comparison of Four High-Sensitivity Immunoradiometric Assays for Thyrotropin and Results of Preliminary Clinical Studies

New immunoradiometric assays (IRMAs) that detect low concentrations of thyroid-stimulating hormone (TSH) have recently become available for routine diagnostic use. These new assays have the putative advantage over conventional radioimmunoassay in that they can distinguish hyperthyroidism from euthyroidism by the finding of a serum TSH below the normal limit. In the present study we sought to evaluate four of these kits according to analytical performance characteristics and clinical utility. All IRM As could detect TSH at a concentration substantially below the lower limit of normal and thus effectively identify hyperthyroid samples. Although differences in the performance characteristics were found, all assays were clearly superior to the conventional radioimmunoassay. It is recommended that IRMAs for TSH be used as routine diagnostic tests for thyroid dysfunction. Their full value in the assessment of hyperthyroidism and other thyroid disorders has yet to be determined

Clinical Value of Calcitonin and Carcinoembryonic Antigen Doubling Times in Medullary Thyroid Carcinoma

Doubling times of basal and stimulated calcitonin (CT) levels and of random carcinoembryonic antigen (CEA) levels were compared over time in 11 patients with residual medullary thyroid carcinoma (MTC)—five with the sporadic MTC and six with the hereditary MTC. Four patients with an indolent form of the disease showed little change in CT levels over three to eight years and little change in CEA doubling times (42 to 70+ months). Seven patients showing rapid progression of disease had CT doubling times of three to 11 months and CEA doubling times of two to 12 months (however, one patient showed no change in CEA). A twelfth patient had a marked increase in CT doubling during two separate periods of pregnancy and lactation. We conclude that both CT and CEA levels may be helpful prognostically in patients with residual MTC, and each should be determined at intervals. Doubling time calculations provide practical estimations whereby the effects of therapeutic approaches, pregnancy, and various environmental influences on the growth of MTC can be evaluated