[Lipid adjustment of alpha-tocopherol concentrations in plasma]

Measurement of alpha-tocopherol concentrations circulating either in plasma or serum is the most common method of measuring the vitamin E status in men. The analytical determination with a suitable HPLC method produces precise and reliable results. The interpretation of the measured alpha-tocopherol values is complicated by the strong positive correlation with different blood lipids. A considerable misinterpretation of the data will occur if these confounding factors are not taken into account by a suitable adjustment. Different methods have been described in the literature which tried to control the confounding effect of blood lipids. These methods were not completely satisfying. Therefore, a mathematical regression model, based on residuals, is introduced and applied to the data of the VERA-study (Verbundstudie Ernährungserhebung und Risikofaktoren Analytik) and the consequences of the lipid-adjustment of the tocopherol values are studied in further statistical procedures. Thereafter, lipid-adjusted tocopherol concentrations can be subjected to more extensive statistical evaluations without the requirement of special stratification.