CLINICAL VALIDATION OF GENEXPERT MTB/RIF ASSAY IN THE RAPID DIAGNOSIS OF EXTRA PULMONARY TUBERCULOSIS

Tuberculosis (TB) remains a significant global health concern, with nearly 2 billion people latently infected worldwide, particularly concentrated in the 30 countries with the highest TB burden, including Pakistan, ranking fifth in this category. Pakistan also grapples with Multidrug-resistant TB strains, complicating treatment options. Early diagnosis is crucial for timely TB treatment initiation and prevention of further transmission. Among various diagnostic tests, the Gene Xpert MTB/RIF assay stands out as a promising tool endorsed by the World Health Organization for diagnosing TB in the lungs and other organs. The current study aims to evaluate the diagnostic performance of this assay in the current setting of Peshawar, Khyber Pakhtunkhwa for the diagnosis of extrapulmonary TB. The study included 529 extrapulmonary specimens from suspected TB patients, meeting the specified criteria, anonymously and consecutively. These specimens underwent decontamination using the NALC-NaOH method and were then inoculated onto Lowenstein Jensen media slants. The remaining pellet from each specimen was subjected to testing using the Xpert assay to detect TB bacilli. The study comprised 529 specimens, including 181 pleural fluid, 117 CSF, 89 tissue biopsies, 84 pus, and 58 ascitic fluid samples. The Xpert assay exhibited an overall sensitivity of 78.3% and a specificity of 92% compared to culture techniques. Its positive predictive value stood at 42.6%, with a negative predictive value of 98.2%. Notably, the sensitivity of the Xpert assay was particularly high for pus and tissue biopsy specimens, while it was moderate for body fluids. Specificity remained consistent across various non-respiratory specimens. The study recommends the use of the Xpert assay for diagnosing extrapulmonary TB in Peshawar, Pakistan, due to its simplicity and very short turnaround time. Despite its moderate sensitivity in body fluids, this can be enhanced by considering additional clinical findings.