Adaptation of TSH filter paper method for regionalized screening for congenital hypothyroidism.

A sensitive, specific, rapid radioimmunoassay is described for the determination of thyrotropin (TSH) in eluates from two 3 mm discs punched from dried blood filter-paper specimens. This method is sufficiently sensitive to easily discriminate between normal infants and infants with primary hypothyroidism. The use of two 3 mm discs enables screening laboratories to easily incorporate this methodology into the currently available, fully automated systems to screen for several metabolic disorders. Since mental retardation occurs in untreated infants with primary hypothyroidism, our TSH method as the primary screening test alone, or in association with a thyroxine (T4) screening test, should detect all infants with primary hypothyroidism with a very acceptable low false-positive recall rate.