A screening procedure for dyslipoproteinemia in the newborn. Apoprotein quantitation on dried blood spots.

A new screening procedure for the detection of dyslipoproteinemia in the newborn is proposed, based on apoprotein quantitation. Blood is collected by heel-prick in infants 5--7 days after birth--when apoprotein and lipids have reached stable values--and adsorbed on filter paper. Blood spots are eluted with a detergent and apoprotein A-I and B are assayed by immunonephelometry. The apo A-I/B ratio is used as a screening parameter, given its high discriminative power between normals and individuals with cardiovascular disease. The quantitation of the apo A-I/B ratio in blood spots is independent of the volume of the blood spot and of the newborn hematocrit. In a follow-up study, plasma lipid and apoprotein concentrations were assayed in the infants with an apo A-I/B ratio lower than 1.0 at 5 days, and a family study was carried out. On screening 1500, 30 infants gave positive results at birth, and were controlled between 2 and 8 months. In eight families studied, six children had abnormally high cholesterol and apo B values and five children had abnormally low HDL cholesterol and apo A-I concentrations. This screening procedure is a new approach to the detection of familial dyslipoproteinemia in the newborn, as it is based on the quantitation of the apo A-I/B protein ratio, instead of cholesterol, LDL cholesterol or beta-lipoprotein quantitation. It enables a differentiation to be made between various forms of dyslipoproteinemia, leads to a better characterization of various diseases, and decreases the percentage of false positive cases.