Biological variability of lipoproteins and apolipoproteins in patients referred to a lipid clinic

We determined the physiological variability of total cholesterol, high- (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, and apolipoproteins A-l and B in fasting blood samples from patients referred to the Johns Hopkins Lipid Referral Clinic. Samples were taken on each of three occasions during baseline evaluation visits before the patients were treated. The median physiological coefficients of variation (CV_P) were as follows: total cholesterol, 5.0%; triglycerides, 17.8%; HDL cholesterol, 7.1%; LDL cholesterol, calculated from the previous three measurements, 7.8%; and apolipoproteins A-l and B, 7.1% and 6.4%, respectively. There were no significant differences in CV_p between children (≤18 years) and adults (>18 years) for any of the measurements. On the basis of our findings, single measurements in serial samples taken on three occasions suffice to establish the patients' usual values with the following precisions (± 1 CV): total cholesterol, ± 4%; triglycerides, ± 11%; HDL cholesterol, ± 8%; LDL cholesterol, ± 6%; and apolipo-proteins A-l and B, ± 7%.