Clinical utility of interferon-γ releases assay (IGRAS) in pott’s disease

Interferon-γ release assays (IGRAs) promised a sensitive and specific diagnosis of latent and active infections of Mycobacterium tuberculosis. Therefore, the intent of this study was to appraise the clinical usefulness of Quantiferon-Gold in Tube (QFT-GIT) for diagnosis of Pott’s disease. We prospectively observed 55 clinical radiological suspected cases of Pott’s disease. They were undergone to the detection of tubercular infection by QFT-GIT, microscopy, culture, polymerase chain reaction (PCR) and histopathological methods.  The sensitivity and specificity of QFT-GIT was calculated against the combined results of performed tests. Patients classified into 2 groups as per anti tubercular treatment (ATT), 24 (43.6%) were new cases (group A) and 31 (56.4%) were relapse / on treatment cases (group B). The positivities among group A and B were; 21 (87.5%) and 19 (61.3%) on QFT-GIT, 10 (42%) and 10 (32.2%) on microscopy, 14 (58.3%) and 13 (54%) on culture, 19 (79.2%) and 18 (58%) on PCR, 21 (87.5%) and 18 (58%) on histopathology. The significant positivities differences (p value <0.05)   among group A and B were found on QFT-G IT and histopathology. Moreover, we found   45 cases as a definite TB and 10 cases were negative by all tests.  Out of these 45 definite TB, 38 cases and out of 10 negative cases two cases detected positive by QFT-GIT. QFT-GIT revealed higher sensitivity in new cases when compared to retreated cases. Its results are also coinciding the combined results of laboratory proven methods and this test is useful in diagnosing of Pott’s disease with 84% sensitivity.