Newborn screening is a worldwide recognised public health measure aimed at the early screening, diagnosis and management of selected inherited diseases. Diseases are selected based on the current ability to detect and treat it and the demonstration of positive economic impact of such interventions. Newborn screening is perhaps the pinnacle of preventative medicine. Early diagnosis and treatment ensures optimal living and allows an individual to contribute to society as opposed to becoming a long term societal responsibility.
There is a perception amongst many South African clinicians that inherited metabolic diseases are exceedingly rare in our country. However, overall estimated incidence for inherited metabolic disease is 1:20001. The March of Dimes global report on birth defects found that genetic and congenital disorders cut across all nations with little regard for ethnic background and socioeconomic status2. All in all there is little evidence to suggest that South Africa is spared from metabolic diseases.
For the past 30 years, the metabolic laboratory on the Potchefstroom Campus of the North West University has received more than 50 000 requests for the metabolic workup of patients. The most frequently occurring metabolic diseases, that are also included in the newborn screening panel, are isovaleric acidaemia, propionic acidaemia, galactosaemia, vitamin B responsive methylmalonic acidaemia, maple syrup urine disease and glutaric acidaemia type I. For many of the diseases in the newborn screening profile, simple and cost-effective treatments are available. The technology and knowhow to perform newborn screening is available and the logistical infrastructure already exists in many instances, albeit predominantly in the private sector. If there is greater support from the private sector, the public sector could be lobbied to offer newborn screening to all South African children.
The ideal time is between 48-72 hours after the first feed but up to a week after birth is still acceptable. The baby needs to have had a few feeds and started the digestion and metabolism of proteins, carbohydrates and fats to bring the disorder to light.
Tests done outside the ideal timeframe will become less accurate. If a metabolic disease is suspected, then specific metabolic testing is required.
Blood is traditionally collected by a heel prick to the baby. Sometimes, instead of a heel prick, blood may need to be drawn from the baby’s vein. 5 drops of blood are needed to be blotted on a Guthrie card.
The screening is then done with tandem mass spectrometry at the metabolomics unit at the North-West University. This is the only lab ion South Africa that is currently doing newborn screening.