Newborn screening for classic galactosemia and primary congenital hypothyroidism in the Nkangala district of the Mpumalanga province of South Africa.

Abstract

Objectives. The main objective of this work was to establish the incidence of classic galactosaemia and primary congenital hypothyroidism in newborns in the Nkangala district of Mpumalanga. In the process a cost-effective protocol for neonatal screening of both diseases was developed. Study design and setting. Blood spot specimens were collected from a third (1 012 out of 3 297) of newborn infants in the Nkangala district of Mpumalanga province from June to November 2005. The specimens were subsequently screened for classic galactosaemia and hypothyroidism using metabolite quantification assays. Galactose-1-phosphate uridyltransferase (GALT) enzyme activity assays were also performed to confirm the reliability of the total galactose assays. The real-time polymerase
chain reaction (PCR) was used to detect commonly occurring mutations in the GALT gene that cause galactosaemia. Thyroidstimulating hormone (TSH) levels were evaluated as a diagnostic metabolite for primary congenital hypothyroidism. Subjects and outcome measures. Informed consent was obtained from the babies' parents before commencement of screening. Total galactose levels above 0.9 mg/l and TSH concentrations above 25.1 mU/l were considered to indicate galactosaemia and hypothyroidism, respectively. A decrease in the total financial input on the screening protocol was evaluated for significance
in cost reduction. Results. The prevalence of hypothyroidism was found to be 0.1%, while none of the newborns presented with classic galactosaemia. There was an up to 20% reduction in direct input costs of screening when our protocol was applied.
Conclusion. Cost-effective newborn screening is possible when classic galactosaemia and congenital hypothyroidism are screened for simultaneously. Cumulative disease frequency plots confirm the already established fact that hypothyroidism tends to occur at higher frequencies than classic galactosaemia.

South African Journal of Child Health Vol. 2 (1) 2008: pp. 19-22