Minoru Kawashima

Semiautomated Enzyme Immunoassay of Thyrotropin as a Mass Screening Test for Neonatal Hypothyroidism

ABSTRACT: A sensitive, simple, and rapid semiautomated sandwich enzyme immunoassay (EIA) was developed for measuring thyrotropin in dried blood samples on filter paper for use in screening for neonatal hypothyroidism. Good correlation was found between values for thyrotropin determined by this method and those determined by radioimmunoassay (RIA) (r = 0.94). In pilot tests on 17,160 newborn infants in the general population, five cases of primary hypothyroidism were detected by both EIA and RIA. The recall rate was slightly higher in EIA than in RIA.

Neonatal Hypothyroid Screening Using Enzymeimmunoassay of Thyrotropin — Comparison with Radioimmunoassay

In order to evaluate a new enzymeimmunoassay (EIA) of thyrotropin(TSH) for neonatal hypothyroidism, 6,100 blood samples on fdter paper, obtained through a neonatal hypothyroid screening program, were examined using a one‐step sandwich EI A and a radioimmunoassay(RIA). Measured TSH values, numbers of cases and false‐positives detected, and recall rates, were compared between the two methods. During this study two cases of congenital hypothyroidism were found by both EIA and RIA. However, a patient with hyperthyrotropinemia was detected only by the EIA. The reproducibility of the EIA was slightly better than that of the RIA. These results suggest that the EIA has same or higher sensitivity for detecting patients compared with the RIA. On the other hand, three cases with falsepositive elevation of TSH by EIA were found. High TSH values by the EIA were likely to be due to transplacental factors, probably immunoglobulin G. Because of high reproducibility of the EIA and false‐positive cases found with it, recall rates of the screening program were slightly higher for the EIA than for the RIA. The recall rate of the EIA could have been decreased by setting a cut‐off point at a higher percentile. Since the EIA is simple to use, this method is suitable for screening for congenital hypothyroidism.