Effects of storage, iron and time of day on indices of lipid peroxidation in plasma from healthy volunteers

The concentrations of thiobarbituric acid reactive substances and conjugated dienes in human plasma are often used as indices of lipid peroxidation. However, concentrations of thiobarbituric acid reactive substances in plasma are markedly affected by the iron content of reagents used in the analysis and by storage of samples at -70-degrees-C. The assay also has a large interbatch coefficient of variation (14%). Plasma concentrations of conjugated dienes are not affected by storage and the coefficient of variation is only 4%. However, there is a marked diurnal variation in levels of conjugated dienes which is similar to the changes in concentrations of plasma triglycerides. Precise standardisation of analytical procedures is required before these assays can be reliably used in clinical medicine.