Yield of pleural biopsy in different types of tubercular effusions

The yield of mycobacteria is shown to be very low in pleural effusions as it is a pauci-bacillary disease. The present study looked at the yield of mycobacterium tuberculosis (MTB) in terms of GeneXpert for acid fast bacilli (AFB) and culture using a medical thoracoscopy guided biopsy and analysed whether the yield increases in more complicated effusions.

This is a retrospective analysis of patients who underwent medical thoracoscopy for tubercular pleural effusions at our institute over the last 5-years. Patients who had no or minimal thin septations were considered as simple effusions and were subjected to semi-rigid thoracoscopy (n = 61). While patients who had multiple loculations and thick septations were considered as complicated effusions and were subjected to rigid thoracoscopy (n = 64). We considered granuloma on a biopsy as the standard for diagnosis of Tuberculosis (TB). Xpert MTB/RIF and The BACTEC MGIT was used for culture.

Out 125 patients with granulomatous inflammation on biopsy, 56 (44.8%) were positive for either GeneXpert or culture for MTB. Only GeneXpert was positive in 43 and only culture was positive in 13. Amongst 61 patients with simple effusion, 14 had either GeneXpert for AFB or AFB culture being positive and 9 out of these patients had GeneXpert for MTB detected on biopsy sample. Only culture was positive in 5 patients. In complicated pleural effusion group either GeneXpert or culture for mycobacterium was positive in 42 (65.6%) out of 64 patients. Only GeneXpert was positive in 34 and culture alone was positive in 8 patients.

The yield of MTB increases as the pleural effusion becomes more complicated. GeneXpert in a biopsy sample is a useful marker for MTB yield especially in a complicated effusion.