[Neonatal screening for congenital hypothyroidism and phenylketonuria].

A newborn screening program for congenital hypothyroidism (CH) and phenylketonuria (PKU) was conducted in 140 163 infants from the Federal District and the states of Mexico and Tlaxcala. These children were born mainly in hospitals for the non-insured population, although some were social security beneficiaries. Their filter-paper blood TSH and phenylalanine concentrations were determined 48 hours after birth. The frequency of CH was 1:1 797, with a 95 per cent confidence interval of 1:1 470 to 1:2 315, and was quite similar in the different types of hospitals. Only two PKU cases were found, for a frequency of 1:70 082, with a 95 per cent confidence interval of 0 to 1:4 762. This work demonstrates the feasibility of newborn screening programs in Mexico, identifies the problems to be solved in order to achieve a wide coverage and establishes the high frequency of CH in the Mexican population.