The yield of different pleural fluid volumes for Mycobacterium tuberculosis culture.

We prospectively compared the culture yields of two pleural fluid volumes (5 and 100 ml) inoculated in liquid culture medium in 77 patients of whom 58 (75.3%) were diagnosed with pleural tuberculosis. The overall fluid culture yield was high (60.3% of cases with pleural tuberculosis). The larger volume had a faster time to positivity (329 vs 376 h, p=0.055) but its yield was not significantly higher (53.5% vs 50%; p=0.75). HIV-positive patients were more likely to have positive cultures (78.9% vs 51.5%; p=0.002).