Serum concentrations of apolipoprotein A-I, apolipoprotein B, and lipoprotein(a) in a population sample

Serum concentrations of apolipoprotein (apo) A-I, apo B, and lipoprotein(a) [Lp(a)] were studied with respect to age and sex in a Finnish population sample of 575 subjects (286 men and 289 women), ages 27-67 years. Apo A-I and apo B were measured with an immunoturbidimetric method calibrated against WHO International Reference Materials. Lp(a) was measured by RIA. Apo A-I and apo B concentrations were almost normally distributed (apo A-I: mean 1.38 g/L vs median 1.34 g/L for men, and 1.58 g/L vs 1.55 g/L for women; apo B: mean 1.21 g/L vs median 1.20 g/L for men and 1.09 g/L vs 1.05 g/L for women). The distribution of Lp(a) was remarkably skewed (mean 190 mg/L vs median 86 mg/L for men, and 169 mg/L vs 85 mg/L for women). The 95% intervals for apo A-I were 1.09-1.84 g/L for men and 1.06-2.28 g/L for women; for apo B, they were 0.63-1.88 g/L and 0.56-1.82 g/L, respectively. Apo A-I concentrations appeared to be unrelated to age, whereas apo B and Lp(a) concentrations were age-dependent. Cutoff values based on the 90th percentile for apo B and the 10th percentile for apo A-I are proposed for identifying subjects at increased risk of coronary heart disease.