TSH AND THYROXINE IN STORED NEONATAL FILTER-PAPER BLOOD SAMPLES FROM PATIENTS WITH CONGENITAL HYPOTHYROIDISM

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Abstract
Filter paper blood samples collected neonatally from infants with congenital hypothyroidism [CH] were analyzed retrospectively for TSH (41) and thyroxine (16). The patients were detected by clinical signs and symptoms and treatment was started during the first 2 yr of life. Similar blood samples from control infants were analyzed for comparison. All CH patients whould have been detected neonatally if screening had been based on TSH analyses with a cut-off limit corresponding to 50 mU of TSH/l of plasma. A screening program involving analyses of thyroxine would require considerably higher recall frequency to yield 100% sensitivity. These results support a nationwide CH screening program based on TSH analyses of phenylketonuria filter paper blood samples using 50 mU/l of plasma as the cut-off limit.