Interpretation of urinary 8-oxo-7,8-dihydro-2′-deoxyguanosine is adversely affected by methodological inaccuracies when using a commercial ELISA

The DNA lesion 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG), a urinary marker of oxidative stress, is produced from reactions of reactive oxygen species with host DNA 2′-deoxyribonucleotides. The current gold-standard assessment is by complex chromatographic methods using HPLC or LC–MS/MS. Several studies have reported that commercial 8-oxodG ELISA kits correlate sufficiently with chromatographic techniques to be an easier alternative for laboratories without access to gold-standard techniques. However, the assumption that significant correlation translates into a similar ability to differentiate disease categories or treatment groups is yet to be tested. Using LC–MS/MS and two variants of a commercial ELISA, we measured urinary 8-oxodG and creatinine concentrations in young children with cystic fibrosis, a disease associated with oxidative stress, and age-matched controls. We show that, despite significant correlation, both ELISAs overestimate the levels of 8-oxodG, and neither ELISA accurately depicted the difference in group means that was observed by gold-standard LC–MS/MS. The implications of these findings for study outcomes add further support for chromatographic techniques, despite their cost and complexity, to remain the gold standard in urinary 8-oxodG assessment.