ELSEVIER Clinica Chimica Acta 227 (1994) 45-57 Factors affecting the thiobarbituric acid test as index of red blood cell susceptibility to lipid peroxidation: a multivariate analysis Domenico Girelli”, Oliviero Olivieri”, Anna Maria Stanzial”, Patrizia Guarini”, Maria Teresa Trevisan b, Antonella Bassi b, Roberto Corrocher*” (Received 21 September 1993; revision received IO February 1994: accepted 2 March 1994) Abstract The relationship between formation of thiobarbituric acid reactive substances (TBARS) in red blood cells (RBC) after exposure to H,O, and factors potentially able to modulate it was _ _ investigated by a multivariate analysis in 92 healthy volunteers. The independent covariates considered were: RBC membrane fatty acids and cholesterol, RBC antioxidant enzymes and zinc, plasma vitamins A and E and serum selenium, zinc and copper. The stepwise multiple- linear-regression analysis revealed RBC membrane fatty acids and cholesterol as predictors of a consistent proportion of the RBC-TBARS variability whereas none of the antioxidant5 entered the equation. The unsaturation index was the most important individual predictor; RBC-TBARS increased with increasing concentrations of total w-3 polyunsaturated fatty acids, C 20:5w-3 and cholesterol, whereas they decreased with increasing concentrations ol total monounsaturated fatty acids, saturated fatty acids, C l6:O and C 18:O. It is suggested that formation of TBARS, at least in currently used conditions. reflects mainly the lipid com- position of the tissue under investigation. without giving sufficient information about the status of the antioxidant defences. * Corresponding author. .4hhrcviurions: GSH-Px. glutathione peroxidase: MDA. malondialdehyde: MUFA. monoumaturated fatty acids; PUFA. polyunsaturated fatty acids: RBC. red blood cells: SFA. saturated fatty acid%: SOD. supcroxide dismutase; TBARS, thiobarbituric acid reactive >ubatances: UI. umaturatlon index. 0009-898l/Y4/$07.00 0 l9Y4 Elsevier Science B.V. All rights reserved SSDI 0009-898 I (94)05822-A