CIRCULATING MARKERS OF FREE-RADICAL ACTIVITY IN PATIENTS WITH PULMONARY TUBERCULOSIS

Setting: Toxic free radicals have been implicated in the development o f lung fibrosis which may be a long-term sequela of pulmonary tubercul osis. Objective: To measure circulating indicators of free radical act ivity in patients with pulmonary tuberculosis in order to determine wh ether patients with active pulmonary TB have elevated levels of circul ating free radical activity, and whether these levels correlated with disease activity as determined by other blood markers of inflammation. Design: 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 chemothera py (8 patients). 3 patients with active lymph node tuberculosis were a lso studied and 4 patients with old lung scarring from previously trea ted tuberculosis had their serum markers analysed. Results: All 3 seru m markers of free radical activity were elevated in patients with acti ve pulmonary tuberculosis. During serial measurement in 8 patients the % molar ratio of 9,11 linoleic acid/9,12 linoleic acid fell progressi vely with treatment. Thiobarbituric acid reactive substances (TBARS) w ere initially elevated in 6/8 patients and remained elevated despite t reatment. 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 patie nts, rose in 4 patients and fell in 1 patient. Conclusions: These resu lts 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 inflamma tory process with fibrogenic potential and that these indicators may b e measuring different stages of the disease process.