|dc.description.abstract||Background: Diagnosis of tuberculous (TB) pleuritis is difficult and better diagnostic tools are needed.
New blood based interferon-gamma (IFN-γ) tests are promising, but sensitivity could be low in HIV
positive patients. The IFN-γ tests have not yet been validated for use in pleural fluid, a compartment with
higher level of immune activation than in blood.
Methods: The QuantiFERON TB®-Gold (QFT-TB) test was analysed in blood and pleural fluid from 34
patients presenting with clinically suspected pleural TB. Clinical data, HIV status and CD4 cell counts were
recorded. Adenosine deaminase activity (ADA) analysis and TB culture were performed on pleural fluid.
Results: The patients were categorised as 'confirmed TB' (n = 12), 'probable TB' (n = 16) and 'non-TB'
pleuritis (n = 6) based on TB culture results and clinical and biochemical criteria. The majority of the TB
patients were HIV infected (82%). The QFT-TB in pleural fluid was positive in 27% and 56% of the
'confirmed TB' and 'probable TB' cases, respectively, whereas the corresponding sensitivities in blood
were 58% and 83%. Indeterminate results in blood (25%) were caused by low phytohemagglutinin (PHA =
positive control) IFN-γ responses, significantly lower in the TB patients as compared to the 'non-TB' cases
(p = 0.02). Blood PHA responses correlated with CD4 cell count (r = 0.600, p = 0.028). In contrast, in
pleural fluid indeterminate results (52%) were caused by high Nil (negative control) IFN-γ responses in
both TB groups. Still, the Nil IFN-γ responses were lower than the TB antigen responses (p < 0.01),
offering a conclusive test for half of the patients. We did not find any correlation between blood CD4 cell
count and IFN-γ responses in pleural fluid.
Conclusion: The QFT-TB test in blood could contribute to the diagnosis of TB pleuritis in the HIV
positive population. Still, the number of inconclusive results is too high to recommend the commercial
QFT-TB test for routine use in pleural fluid in a TB/HIV endemic resource-limited setting.||en