Oxidative stress markers in tears of patients with Graves' orbitopathy and their correlation with clinical activity score

Background: To investigate the concentrations of oxidative stress markers, 8-hydroxy-2-deoxyquanosine (8-OHdG) and malondialdehyde (MDA), in tears and their correlation with the clinical activity score (CAS) in patients with Graves' orbitopathy (GO) according to disease activity. Methods: We recruited 27 participants with inactive stage GO, 35 participants with active stage GO, and 25 healthy controls without GO. The tear concentrations of 8-OHdG and MDA were determined by enzyme-linked immunosorbent assay. The correlation between CAS and the concentrations of tear 8-OHdG and MDA were analyzed according to the disease activity in the GO patients. Results: The levels of 8-OHdG and MDA were 56.30+/-16.81 ng/mL and 5.39 +/- 1.31 pmol/mg, respectively, in the control subjects, and 123.46 +/- 22.67 ng/mL and 13.59 +/- 3.93 pmol/mg, respectively, in patients with inactive stage GO, and 215.14 +/- 35.61 ng/mL and 22.52 +/- 4.63 pmol/mg, in patients with active stage GO. The mean concentrations of 8-OHdG and MDA were higher in patients with inactive and active stage GO compared with the control group (all P<0.001). Furthermore, in the active stage group, tear concentrations of 8-OHdG and MDA were higher than those in the inactive stage group (all P<0.001). The level of 8-OHdG (r=0.676, P<0.001) and MDA (r=0.506, P=0.002) correlated with CAS in the active stage GO group. Conclusions: The concentrations of 8-OHdG and MDA in tears increased in patients with GO, especially in those in the active stage. In patients with active stage GO, CAS correlated significantly with the tear 8-OHdG and MDA levels.