Neonatal screening for congenital hypothyroidism in Mexico: experience, obstacles, and strategies

Objective-To report the experience, obstacles, and strategies of screening for congenital hypothyroidism. Setting-Newborns in Mexico. Methods-Thyroid stimulating hormone (TSH) was measured by enzyme immunoassa y using commercial kits in 1 140 364 newborns. Results-There were 464 positive cases, of whom 299 (64.4%) were girls. 236 (50.9%) showed ectopic nodules, 202 (43.5%) thyroid agenesis, 21 (4.5%) dys hormonogenesis, and 5 (1.1%) an unclassified goitre. The false positive rat e was 0.024% and there were 11 false negative results. Currently, 600 000 ( 26%) of the 2 300 000 newborns are screened. This percentage has been incre ased in recent years by taking samples from cord blood and will be increase d further by starting congenital hypothyroidism screening at social securit y units and by midwives screening infants born at home. Conclusions Mental retardation in infants in developing countries can be re duced by neonatal screening, and carefully planned strategies can steadily extend the benefits of screening.