Specimen Dilution for C2 Monitoring with the Abbott TDxFLx Cyclosporine Monoclonal Whole Blood Assay

logic studies. The II for men and women separately were not different from the II of the reference population. This provides objective evidence that stratified reference inter- vals according to gender are unnecessary. At 95% confi- dence, the reference change value of plasma total iPF2-III was 72.9%, suggesting that relatively large differences between the results of sequential specimens would be required for them to be significantly different. Our finding of a wide biological variation in the plasma total iPF2-III concentration has not been reported previ- ously. Helmersson and Basu (9 ) reported a large variation in the urinary excretion of iPF2-III in healthy individuals with a mean CV of 42% over 10 consecutive days. Both plasma and urinary iPF2 have been used as markers of in vivo lipid peroxidation, but there is a lack of correlation between plasma and urinary iPF2 concentration (10 ). To understand the wide biological variation of plasma total iPF2-III concentrations in healthy nonsmokers, other factors can also be considered. Diet should not be a contributing factor; it has been reported that diet does not confound plasma total iPF2-III values in humans (11 ). Physical exercise can create an imbalance between oxi- dant and antioxidant concentrations. A recent study showed that extreme endurance exercise is associated with increased production of plasma iPF2, but moderate exercise such as walking is unlikely to represent a con- founding factor (12 ). Extreme endurance exercise had not been documented in our study group. More studies are required to understand the observed wide variation. In summary, we present new data relating to plasma total iPF2-III and the plasma iPF2-III/AA ratio. To our knowledge, this is the first report on the biological vari- ation of plasma total iPF2-III. These data are important for the assessment of individuals and the design of studies involving these variables.