Neonatal screening for hypothyroidism at a university hospital in Thailand

Neonatal screening is an essential program for early identification of congenital hypothyroidism. Between July 1991 and May 1998, 37, 262 infants born at Chulalongkorn Hospital were enrolled to the screening program. Blood TSH levels were determined on infants at > or = 48 hours after birth. They were performed in dried blood sample taken by heel prick on filter papers. TSH levels were measured by fluoroimmunoassay from July 1991 to December 1997 and by immunoradiometric assay from January to May 1998. Infants with TSH screening level higher than the cut off level (20 mu/l) were recalled for re-evaluation which consist of complete physical examination and blood test for serum T4 and TSH. Bone age determination and thyroid scan using technetium-pertechnetate were performed if the serum T4 and TSH levels were abnormal. The recall rate was 0.28% and response rate was only 69%. Primary congenital hypothyroidism was diagnosed in 15 infants. Prevalence was 1: 2,484. Among these infants, 8 had ectopic thyroid, 3 had normal glands and 3 were athyrotic. One infant died before the thyroid scan could be performed and did not receive treatment. The median age at initiation of thyroxin therapy was 29 days (range, 20-67 days). The follow up result was satisfactory. This study demonstrated the potential vulnerability of congenital hypothyroid screening program in Thailand. Improvement of parents' education, communication and monitoring should be emphasized for a large screening program.