Abstract

It is known that lymphokines produced by T-lymphocytes increase the bactericidal activity of macrophages against mycobacteria, and most likely, interferon gamma (IFN-g) is the main T- lymphocyte product responsible for this ac-tion. IFN-g level is found higher than 5 IU/ ml almost in all tuberculous pleural effusions, but specificity is not so high. The aim of this study was to determine the value of pleural fluid/ serum ratio (PF/S) of IFN-g to improve the accuracy of diagnosis.

We studied 79 patients with pleural effusion who were classified according to their diagnosis into four groups; tu-berculosis- TB (24), malignancy (23), transudates (17) and miscellaneous group (15). PF and S IFN-g levels were me-asured in all groups and also PF/S ratios of IFN-g were calculated.

Although there were no significant differences between all groups comparing serum IFN-g levels, the mean PF IFN-g level of TB group was significantly higher than other groups (p<0.0001). Similarly, the mean PF/S ratio of IFN-g was significantly higher in TB group than the others (p<0.0001).

A cut-off value 5 IU/ ml for PF IFN-g and a cut-off value 20 for PF/S ratio of IFN-g easily distinguished tubercu-lous effusions from other types of pleural effusions. Also we demonstrated that with the use of two parameters toget-her, all of pleural effusions could be correctly classified as either TB or non-TB.

We conclude that PF/S ratio of IFN-g is valuable parameter for diagnosis of tuberculous pleural effusions and the use with PF IFN-g together will improve the accuracy of diagnosis.