Tuberculous pleural effusions: increased culture yield with bedside inoculation of pleural fluid and poor diagnostic value of adenosine deaminase.

A prospective study of 111 adult patients with a pleural effusion was carried out in an area with a high prevalence of tuberculosis to compare the yield of bedside with laboratory inoculation of pleural fluid, and the yield and speed of a radiometric mycobacterial culture system (BACTEC) with that of conventional culture. The use of adenosine deaminase activity in pleural fluid as a diagnostic test for tuberculosis was also evaluated. In the 62 cases of tuberculosis confirmed histologically or by culture, or both, the BACTEC system had the same culture yield as conventional mycobacterial culture (positive in 14 cases-23%), but was significantly faster (18 versus 33 days). Bedside inoculation had a culture yield significantly higher than laboratory inoculation in the 24 patients tested (11 versus four). The remaining three diagnostic categories were malignant (28), miscellaneous (10), and undiagnosed (11). Median adenosine deaminase activity was significantly higher in tuberculous effusions than in any of the other categories, but there was considerable overlap between the groups. It is concluded that the BACTEC system is significantly faster than conventional mycobacterial culture and that bedside inoculation of pleural fluid substantially increases culture yield. Adenosine deaminase does not provide as valuable a diagnostic test of pleural tuberculosis as has been suggested.