Dheda, Keertan and Zyl-Smit, Richard N. van and Sechi, Leonardo Antonio and Badri, Motasim and Meldau, Richard and Symons, Gregory and Khalfey, Hoosein and Carr, Igshaan and Maredza, Alice and Dawson, Rodney and Wainright, Helen and Whitelaw, Andrew and Bateman, Eric D. and Zumla, Alimuddin (2009) Clinical diagnostic utility of IP-10 and LAM antigen levels for the diagnosis of tuberculous pleural effusions in a high burden setting. PLoS One, Vol. 4 (3), e4689. ISSN 1932-6203. Article.
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Background: Current tools for the diagnosis of tuberculosis pleural effusions are sub-optimal. Data about the value of new
diagnostic technologies are limited, particularly, in high burden settings. Preliminary case control studies have identified
IFN-γ-inducible-10kDa protein (IP-10) as a promising diagnostic marker; however, its diagnostic utility in a day-to-day clinical
setting is unclear. Detection of LAM antigen has not previously been evaluated in pleural fluid.
Methods: We investigated the comparative diagnostic utility of established (adenosine deaminase [ADA]), more recent
(standardized nucleic-acid-amplification-test [NAAT]) and newer technologies (a standardized LAM mycobacterial antigendetection
assay and IP-10 levels) for the evaluation of pleural effusions in 78 consecutively recruited South African
tuberculosis suspects. All consenting participants underwent pleural biopsy unless contra-indicated or refused. The
reference standard comprised culture positivity for M. tuberculosis or histology suggestive of tuberculosis.
Principal Findings: Of 74 evaluable subjects 48, 7 and 19 had definite, probable and non-TB, respectively. IP-10 levels were
significantly higher in TB vs non-TB participants (p<0.0001). The respective outcomes [sensitivity, specificity, PPV, NPV %]
for the different diagnostic modalities were: ADA at the 30 IU/L cut-point [96; 69; 90; 85], NAAT [6; 93; 67; 28], IP-10 at the
28,170 pg/ml ROC-derived cut-point [80; 82; 91; 64], and IP-10 at the 4035 pg/ml cut-point [100; 53; 83; 100]. Thus IP-10,
using the ROC-derived cut-point, missed ~20% of TB cases and mis-diagnosed ~20% of non-TB cases. By contrast, when a
lower cut-point was used a negative test excluded TB. The NAAT had a poor sensitivity but high specificity. LAM antigendetection
was not diagnostically useful.
Conclusion: Although IP-10, like ADA, has sub-optimal specificity, it may be a clinically useful rule-out test for tuberculous
pleural effusions. Larger multi-centric studies are now required to confirm our findings.
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