10] Assessing variability in quantitation of carotenoids in human plasma: Variance component model

Abstract

This chapter describes a variance component model, which can be used to identify the sources of technical variability and to assign the relative contribution of each of these sources to the overall variability in the method for quantitating β -carotene in human plasma. Although β -carotene was analyzed in this system, the method presented in the chapter for determining technical variability in a multistep preparation assay can be applied to the analysis of other compounds found in plasma that require extensive sample processing. In addition, problems unique to the assay of carotenoids in plasma, including standardization, are discussed in the chapter. Using a variance components model, the variance for each major source of variability in the assay of β -carotene from human plasma, including effects of day and numbers of aliquots, extractions, and injections is estimated. This method provides a mechanism to identify sources of variability in the assay of micronutrients so that procedures may be modified accordingly prior to undertaking the analysis of large numbers of biological samples.