Serum indicators of free radical activity in idiopathic pulmonary fibrosis.

Serum levels of free radical activity were measured in 37 patients with idiopathic pulmonary fibrosis (IPF) and 16 control subjects. Three assays used were (1) simultaneously measured levels of the 9,11-diene conjugate of linoleic acid and 9,12-linoleic acid expressed as a percent molar ratio (%MR), a measure of free-radical-mediated lipid peroxidation; (2) thiobarbituric acid reactive substances (TBARS), one of which is malondialdehyde; (3) desferrioxamine-chelatable iron assay, a measure of the potential iron available to catalyze free radical generation. Mean %MR, TBARS and desferrioxamine-chelatable iron were all elevated initially in patients with IPF compared with control subjects (%MR, p < 0.0001; TBARS, p = 0.0013; desferrioxamine-chelatable iron, p = 0.0029). Furthermore, the serum %MR was higher in a subset of patients with clinically worsening IPF than in those patients with clinically stable disease (p = 0.002). Treatment did not appear to affect the three different serum indicators of free radical activity. Thus, lipid peroxidation appears to be increased in patients with IPF and is associated with an increase in desferrioxamine-chelatable iron levels. Serum % MR levels appeared to correlate with clinical disease activity, and they may have a role in monitoring disease activity.