Evaluation of real-time polymerase chain reaction, interferon-gamma, adenosine deaminase, and immunoglobulin A for the efficient diagnosis of pleural tuberculosis

Abstract

Pleural tuberculosis (TB) is a diagnostic challenge because of its non-specific clinical presentation and paucibacillary nature. Conventional diagnosis methods have limitations. We evaluated the real-time polymerase chain reaction (PCR), interferon-gamma (IFN-γ), adenosine deaminase (ADA), and immunoglobulin A (IgA). We assessed 204 cases: 50 were confirmed pleural TB, 104 were probable pleural TB, and 50 formed the non-TB group. IFN-γ and IgA were measured by enzyme-linked immunosorbent assay and ADA was measured by colorimetric assay. Real-time PCR was carried out using the 16S rRNA sequence, pleural biopsy specimens were submitted to histopathologic examination, pleural fluid culture was undertaken using Lowenstein-Jensen and MGIT-BACTEC, and pleural fluid smears were stained with auramine O. For confirmed and probable pleural TB cases, the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was highest for IFN-γ (0.994 and 0.963, respectively), followed by ADA (0.989 and 0.945, respectively), real-time PCR (0.898 and 0.784, respectively), and IgA (0.817 and 0.784, respectively). For confirmed and probable pleural TB cases, IFN-γ showed the highest sensitivity (98% and 76.9%, respectively), followed by ADA (92% and 73%, respectively), real-time PCR (80% and 57.7%, respectively), and IgA (70% and 57.7%, respectively). With regard to combined positivity, the combination of 'either real-time PCR or IFN-γ' showed the highest sensitivity: 100% in confirmed pleural TB and 96.2% in probable pleural TB. IFN-γ showed the highest sensitivity as an individual diagnostic test. When a combination of tests was used, positivity of 'either IFN-γ or real-time PCR' appeared valuable for the diagnosis of pleural TB.