Improved method for the immunological detection of malondialdehyde-modified low-density lipoproteins in human serum

Oxidized low-density lipoproteins (ox-LDL) such as malondialdehyde-modified LDL (MDA-LDL) play an important role in the pathogenesis of atherosclerosis. This study is aimed to establish a standard enzyme-linked immunosorbent assay (ELISA) for measuring serum MDA-LDL, and evaluate its usefulness by analyzing serum samples of diabetes mellitus (DM) patients. Serum sample stability, analytical sensitivity, intra- and inter-assay precision, dilution linearity, supplementation and recovery, and interfering substances were examined. Normal reference levels in 86 healthy subjects (33 males and 53 females; average age 34.4±7.8 years) with normal lipid profiles were also determined. MDA-LDL levels in blood and serum were unstable and gradually increased during storage. However, it could be stabilized by the addition of a reagent, which included sucrose. The detection limit of the assay was 6.3 U/l. Intra- and inter-assay imprecisions were