[Microdetermination of TSH in dried blood spot--its use in the mass-screening for congenital or juvenile primary hypothyroidism (author's transl)].

Blood TSH (Thyroid Stimulating Hormone) was successfully measured by radioimmunoassay in a dried blood spot on filter paper which is obtained in newborn screening for metabolic disorders. By this method, the minimal detectable level of blood TSH was about 10 muU/ml, which is the approximate upper limit of normal values of blood TSH. Good correlation was found between the TSH values obtained from this specimen and from liquid serum samples from the same subjects. The duplication of assay of a single sample was not necessary. A screening program using the method described here was initiated and a 4 year old infant was found to have primary hypothyroidism, later verified by other testing methods. Since the technique is simple and adequately sensitive for the detection of hypothyroidism, it could be a valuable method for use in mass-screening of newborns for congenital hypothyroidism.