Intra-individual variation of plasma lipids and lipoproteins in prepubescent children

Estimates of the average intra-individual biological variability for plasma lipids and lipoproteins differs substantially among published studies. Mor eover, this topic does not appear to have received consideration in exercis e and health literature with normal, healthy children as subjects. The purp ose of this study was, therefore, to determine the short-term day-to-day va riability of the lipid-lipoprotein profile from 19 children [mean (SD), 11. 5 (0.8) years] from 3 separate venous blood samples. Intra-individual stand ard deviations, variances and coefficients of variance were determined for total cholesterol (TC), triacylglycerol (TG), high-density lipoprotein-chol esterol (HDL-C), HDL-C sub-fractions HDL2 and HDL3, and low-density lipopro tein-cholesterol (LDL-C). The intra-individual variation for TC and LDL-C w as used to calculate the 95% confidence intervals (CIs) around the National Cholesterol Education Programme (NCEP 1991) cut-off points. The main findi ng was that all of the measured blood analytes including TC, TG, HDL-C, HDL 2, HDL3, and LDL-C varied considerably from day-today. Coefficients of tota l variation ranged from 3.5% for HDL3 to 25.4% for TG. Classification of in dividuals using NCEP guidelines was difficult based on only one or two bloo d samples. The magnitude of variation for LDL-C meant that a 95% CI could n ot be constructed around the NCEP borderline-high classification from eithe r one or two samples. However, averaging three TC and LDL-C measurements in creased the likelihood of classification within the 95% CI. The results ind icate that when using the NCEP guidelines for children and adolescents, tru e concentrations for TC and LDL-C should be based on the mean of multiple s amples.