OK, I know that doesn’t perfectly rhyme. Thank you to Kendra and Nathan for presenting an outstanding case of a patient with a recurrent pleural effusion, found to have calcified granulomas in the bilateral upper lobes, and a high suspicion for TB pleurisy.
Tuberculous Pleural Effusion (i.e. TB Pleurisy):
- Globally, MTB is the most common cause of pleural effusion!
- Extrapulmonary TB accounts for about 25% of the initial presentations, most frequently involving lymph nodes and pleura
- Gold Standard: detection of M. tuberculosis in sputum, pleural fluid, or pleural biopsy specimens either by microscopy and/or culture or histological demonstration of caseating granulomas in the pleura along with AFB
- Often, diagnosis is inferred in patients who present with a lymphocytic predominant exudate + high ADA level
- It is important to obtain cultures on induced sputum samples, even in the absence of obvious parenchymal involvement.
- At this time, there are no studies evaluating the role of sputum nucleic acid amplification (NAA) molecular studies such as Xpert MTB/RIF in the context of TB pleural effusions.
- NAA tests may increase the diagnostic yield of sputum compared with conventional microscopy, but is unlikely to be more sensitive than culture
- Uniformly exudative effusions, typically with >50g/L of protein, LDH elevated in 75% of cases (typically >500)
- ADA: Wide range of cut-offs but the higher the value the more liekely.
- Accurate threshold in variety of studies suggests 40-60 U/L
- Note that the local prevalence of TB greatly affects the performance of the ADA test
- Specifically, in low prevalence areas/population, a negative test can be pretty good at ruling out TB
- Presence of caseating granulomas with AFB on histological exam is a SLAM dunk, although seeing AFB is not required in high burden areas
- The more biopsies the higher the sensitivity, and performing with thoracoscopy greatly increases the sensitivity