An avidin-biotin amplified ELISA for thyrotropin in human serum. Its implication for routine determination of thyrotropin in developing countries

Abstract

In developing countries the acquisition and use of radioisotopes with their short shelf lives poses enormous problems. The objective of this study was to develop a simple, sensitive, non-isotopic method for the measurement of TSH in human serum. A conventional sandwich enzyme-linked immunosorbent assay (ELISA) technique was modified to incorporate the avidin-biotin complex (ABC) in order to enhance the sensitivity of a solid-phase micro-ELISA for TSH. The lower limit of TSH detectability was 0.2 mIU/l. TSH levels ranged from 0.3 to 5.1 mIU/l in euthyroid subjects, 11.5-98.0 mIU/l in hypothyroid subjects and less than 0.2-2.1 mIU/l in hyperthyroid subjects. Sera from euthyroid post-menopausal or pregnant women yielded TSH levels within the normal range. The correlation between the TSH values obtained in the ELISA-ABC and a sensitive commercial immunoradiometric method was high (n = 59, r = 0.980, P less than 0.01). The simplicity and relatively high sensitivity of the procedure should make it a method of choice for TSH determination in small hospitals and those in developing countries.