Measurement of apolipoprotein B as a screening test for identifying children with elevated levels of low-density lipoprotein cholesterol.

We compared the efficacy of two screening tests, measurement of apolipoprotein B (apo B) levels and measurement of serum total cholesterol levels, in detecting elevated low-density lipoprotein cholesterol (LDL-C) values in children. We studied 2850 children, aged 5 to 17 years, who had fasting lipid, lipoprotein, and apolipoprotein levels measured as part of the Bogalusa Heart Study. The test characteristics of apo B were superior to those of serum total cholesterol in screening children to detect elevated levels of LDL-C (greater than or equal to 95th percentile) and moderately elevated LDL-C levels (greater than or equal to 80th percentile). Unusually high or low values of high-density lipoprotein cholesterol are responsible for most of the misclassification that occurs when measurement of total cholesterol is used as a screening test for identifying children with elevated levels of LDL-C. This confounding effect of high-density lipoprotein cholesterol was eliminated when measurement of apo B levels was used as a screening test. Because the apo B test is more specific at a given sensitivity than the total cholesterol test, the apo B test can cost more and still be less expensive as a screening strategy. As the methods for determining apolipoprotein levels become standardized and readily available, the measurement of apolipoproteins could be developed into superior screening tests for the identification of patients with dyslipidemias.