Neonatal screening for hyperlipoproteinemia. Methods for direct estimation of cord serum VLDL + LDL.

The early detection of hyperlipoproteinemia in newborn infants has so far been based upon estimation of cord blood total lipids (cholesterol and triglyceride) and lipoprotein-lipids (VLDL-, LDL- and HDL-cholesterol). To be able to make a direct estimation of cord serum beta-lipoproteins (VLDL + LDL) two quite different methods were modified, one immunological and the other turbidimetric. Good correlations were found to VLDL- + LDL-cholesterol isolated in the ultracentrifuge (r = 0.848 and 0.831, respectively). If neonatal screening for hyperlipoproteinemia is considered, we recommend the very easy and inexpensive turbidimetric method. Furthermore, using cord serum, two conventional precipitation methods with heparin-CaCl2 and heparin-MnCl2 were compared by ultracentrifugation and high correlations were found (r = 0.923 and 0.899, respectively). A clamping study showed that following early clamping of the cord, the concentration of cord serum lipids and lipoproteins did not change markedly within the first five minutes. Storing experiments showed that serum should be separated within the first 12 h to avoid unpredictable changes in the concentration of cord serum lipids and lipoproteins.