Neonatal apo A-I, apo B, and apo(a) levels in dried blood spots in an Australian population.

We measured neonatal apo A-I and apo B by ELISA, and apo(a) by RIA, in capillary blood spotted onto filter paper in samples also used for routine neonatal screening in 1032 consecutively born babies. In the 2- to 5-d-old babies with birth weights greater than or equal to 2.0 kg (n = 919), mean +/- SD levels of apo A-I and B were 0.48 +/- 0.19 g/L and 0.24 +/- 0.14 g/L of whole blood, respectively. The apo A-I levels were affected by birth weight (negatively) and by age at sampling (positively). The apo B levels were affected positively by both variables, and girls had higher levels than boys (p less than 0.01). These variables accounted for 3.5 and 6.2% of apo A-I and apo B variability, respectively (p less than 0.001). The apo(a) levels (mean +/- SD, 20 +/- 23 U/L; median, 14 U/L, n = 1032) were unaffected by these factors. After adjustment for these variables, apo A-I levels were nearly normally distributed, whereas those of apo B were still positively skewed. The apo(a) distribution was strongly positively skewed and 1.2% of babies had levels above the equivalent of 25 mg/dL of lipoprotein(a) in serum. Our study shows that blood spots can be used to estimate apo A-I, apo B, and apo(a) levels in neonates, and establishes normal ranges. The results suggest that the apo(a) gene is expressed during the 1st postnatal week and that levels are independent of birth weight and apo A-I and B concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)