Nutritional considerations in the variability of plasma cholesterol measurements

The concentration of plasma cholesterol is influenced by biological factors as well as clinical and analytical ones. Day-to-day variation can provide a misleading estimate of plasma cholesterol as it can differ by up to 12%. Seasonal variations occur with elevated concentrations in (northern hemisphere) winter relative to summer, possibly due to diet and life-style influences. Clinical and analytical factors also contribute to the variation. These include the manner with which blood is collected, the nutritional state of the subject and subsequent specimen handling. Analytical factors such as the effectiveness of the reagents and controls chosen, as well as the extent of interference by agents of metabolic or dietary origin, can introduce a bias into the analysis. More control can be exerted over the clinical and analytical factors compared with biological variation.