Day-to-day variability and analytic error in determinations of lipids in children.

In a pilot study, short-term (Monday, Wednesday, and Friday of the same week) variability of cholesterol and triglycerides in serum and in very low-density, low-density, and high-density lipoproteins were studied in 10 children aged 6 to 16. All of the subjects had normal levels of cholesterol and triglycerides. Analytic error was determined by blinded triplicate analyses of a fourth specimen from five of the same subjects. In the triglycerides, except for the smallest fraction (high-density), the differences from day to day in the same child were larger than the differences between children. The results indicate that single determinations of whole serum triglyceride carry limited significance since, within the week, the level may well change by a factor of two.