Circulating markers of free radical activity in patients with pulmonary tuberculosis

Toxic free radicals have been implicated in the development of lung fibrosis which may be a long-term sequela of pulmonary tuberculosis.

To measure circulating indicators of free radical activity in patients with pulmonary tuberculosis in order to determine whether patients with active pulmonary TB have elevated levels of circulating free radical activity, and whether these levels correlated with disease activity as determined by other blood markers of inflammation.

17 patients with active pulmonary tuberculosis were studied. Serial serum levels of 3 assays of free radical activity were measured at diagnosis (17 patients), and over a 2-7 month period on chemotherapy (8 patients). 3 patients with active lymph node tuberculosis were also studied and 4 patients with old lung scarring from previously treated tuberculosis had their serum markers analysed.

All 3 serum markers of free radical activity were elevated in patients with active pulmonary tuberculosis. During serial measurement in 8 patients the % molar ratio of 9,11 linoleic acid/9,12 linoleic acid fell progressively with treatment. Thiobarbituric acid reactive substances (TBARS) were initially elevated in 6/8 patients and remained elevated despite treatment. In 2 patients TBARS were in the normal range at presentation but subsequently rose with treatment. Desferrioxamine-chelatable iron was initially normal in all but 1 patient, remained normal in 2 patients, rose in 4 patients and fell in 1 patient.

These results suggest that increased circulating levels of free radical activity are found in active pulmonary tuberculosis and hence may play a role in the resultant fibrosis. It also reinforces the belief that a range of free radical activity (FRA) indicators are produced in any inflammatory process with fibrogenic potential and that these indicators may be measuring different stages of the disease process.