Experience in neonatal screening for congenital hypothyroidism.

From November 1986 to June 1991, 91,683 neonates were screened for congenital hypothyroidism by measuring thyroid-stimulating hormone (TSH). 10,284 neonates were screened with chemical luminoimmunoassay (CLIA), and 80,399 screened with time-resolved fluoroimmunoassay (DELFIA). The critical value of TSH was 20 mU/L. Twenty cases were confirmed to be congenital hypothyroidism. The incidence was 1:4584, with a female to male ratio of 3:2. These patients were treated with thyroid gland desiccant, with a dosage equivalent to L-thyroxin 5-7.5 micrograms/kg/day. Their physical growth and intellectual ability were normal. 81,201 dried blood specimens were tested in single for TSH by DELFIA and T4, T3 and TSH serum testing for those with elevated TSH. No false negative and missing case was found after the screening program started. When frequent fluctuation of T4 and TSH concentration occurred at normal level in some infants, it is better to wait and have a close observation, however the treatment must be started before 3 months of age to avoid the risk of mental retardation.