Oxidative stress has been implicated in coronary artery disease (CAD). Malondialdehyde (MDA) is lipid
peroxidation end product. Bilirubin may act as an antioxidant that suppresses lipid oxidation. The role
of MDA and antioxidant capacity and their inter-relationship in patients with and without CAD was
investigated. Thirty-eight consecutive patients with angiographically diagnosed CAD were compared
with 60 age, and sex-matched controls. The controls had completely normal coronary arteries in
angiograms. Plasma MDA, serum bilirubin, total homocysteine and total antioxidant capacity (TAC)
levels were measured. Risk factors of CAD were determined for all subjects using National Cholesterol
Education Program (NCEP)-Adult Treatment Panel (ATP)-III criteria. Serum MDA and total homocysteine
concentration were significantly higher, but TAC, total bilirubin and direct bilirubin levels were lower in
CAD patients when compared to the controls. Age, and sex-adjusted plasma MDA levels had negative
correlations with TAC (r = -0.30, p = 0.001) and total bilirubin (r = -0.30, p = 0.002) concentrations. In
multivariate analysis by the multiple logistic regression method, serum MDA was significantly
associated with CAD (OR = 1.15, 95% CI, 1.25 to 1.82; p < 0.0001)) after adjustment for lipid status
parameters and traditional risk factors in this study population. Increased serum MDA concentration, as
a biomarker of lipid peroxidation, low serum bilirubin and antioxidant capacity were observed in
patients with angiographically defined CAD. The significant inverse correlation of the serum bilirubin
and MDA levels demands further in-depth investigations to clarify the association between them in the
development of CAD
