Comparison of analyses of urinary 8-hydroxy-2′-deoxyguanosine by isotope-dilution liquid chromatography with electrospray tandem mass spectrometry and by enzyme-linked immunosorbent assay

A highly sensitive and selective method, using isotope-dilution liquid chromatography with tandem mass spectrometry (LC/MS/MS), for quantification of urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), an important biomarker of oxidative stress, was developed and compared with a method using an enzyme-linked immunosorbent assay (ELISA). The synthesis of 15N 5-8-OHdG is described. In this study, 140 urine samples were collected from workers in a coke oven plant, including samples from 49 control workers and 91 workers who had been occupationally exposed to polyaromatic hydrocarbons (PAHs). The major urinary metabolite of PAHs, 1-hydroxypyrene (1-OHP), was measured for the exposed workers. Results from the present study showed a significant correlation between these two measurements for determination of 8-OHdG (p < 0.05, r2 = 0.70). However, only the LC/MS/MS measurements of urinary levels of 8-OHdG showed a significant difference between the exposed and the control subjects (p<0.05). The ELISA method failed to demonstrate this difference. Furthermore, only by using the LC/MS/MS method was a significant correlation observed between the urinary levels of 1-OHP and 8-OHdG. These findings suggest that a highly specific and sensitive analytical method such as isotope-dilution LC/MS/MS is extremely important and necessary for accurate measurement and a comprehensive study of oxidative stress in human subjects.