Variability of total cholesterol concentrations in serum by repeated measurements in a large pediatric population--limitations of quality controls for laboratory analyses.

Abstract

Abstract We evaluated the variability in total cholesterol concentrations in serum in a large population of children over a period of time, to help us discern the limitations in reliability of current clinical laboratory methods for its analysis. We analyzed sera from a population of approximately 4000 children over a four-year period, quality-control sera, pooled sera, and surveillance samples from the Centers for Disease Control over a seven-year period, with a Technicon AutoAnalyzer II. Two methods of correction were suggested to adjust deviations in yearly serum total cholesterol means: yearly screening data were corrected on the basis of monthly variability in pooled-serum determinations and on the basis of deviations from values suggested by the Centers for Disease Control. Both correction methods were insufficient. These changes occur very slowly, and unless there is close monitoring and frequent comparison with a known standard, changes in laboratory results still can occur.