Recent Progress in Neonatal Mass Screening for Congenital Hypothyroidism and Adrenal Hyperplasia Using Enzyme Immunoassays

Abstract

This chapter describes various enzyme immunoassays for thyroid-stimulating hormone (TSH), thyroxin (T4), free T4, and 17α-hydroxyprogesterone (17-OHP) that have been developed in the laboratory and their applications to neonatal mass screening for congenital hypothyroidism (CH) and congenital adrenal hyperplasia (CAH). Neonatal hypothyroid screening by radioimmunoassay (RIA) shows its utility and effectiveness, the RIA procedure has many associated disadvantages, such as requirements for legal regulation of RI laboratories, high costs of automatic instrumentation, short half-life of 1251-labeled compounds, difficulty of discarding contaminated compounds, and problems related to radiation hazards. EIA method was developed using alkaline phosphatase as label for the assay of TSH in dried blood on filter paper. It develops a fluorescent EIA for measurement of TSH in serum using Sepharose 4B as the solid phase to separate the bound and free fractions. ELISA methods for T4 and FT4 are established for simultaneous TSH-T4 determinations or as complementary tests for CH mass screening. Enzyme-linked immunosorbent assay (ELISA) methods for TSH, T4, FT4, and 17-OHP have the advantages of high sensitivity, rapidity, ease of use, and low cost compared to the usual RIA methods and are useful in neonatal mass screening for CH and CAH.