Screening for congenital hypothyroidism - results from a pilot study in Stockholm

Abstract

During one year a pilot study was carried out in Stockholm in order to define optimal conditions for routine nationwide screening for congenital hypothyroidism. About 20.000 children were born and all participated in the study. Part of their PKU samples were used, i.e. dried blood on filter paper collected on the fifth day of life. Each sample was analyzed for both T4 and TSH. Children with T4 levels below - 2 SD of the mean and/or TSH levels above 30 mU/1 of plasma were recalled for clinical investigation and additional laboratory studies. However, preterm infants were recalled only if the concentration of TSH was increased. A total of 160 newborns (=0.8%) were thus considered to have positive screening results. Among these 6 children were identified with primary hypothyroidism, one with secondary hypothyroidism and 7 with hypo-TBG-emia. Based on the results obtained we suggest that a nationwide screening program for congenital hypothyroidism should be based on the PKU blood sample and TSH analyses. With 50 mU of TSH/1 of plasma as the cut off limit the false positive recall rate will be less than 0.1 % and the risk of false negative results will be minimal. The present study was approved by the ethical committee of the Karolinska Institute.