Diagnostic Efficacy, Sensitivity, and Specificity of Xpert MTB/RIF Assay for Spinal Tuberculosis and Rifampicin Resistance

Study Design. A cross-sectional observational study. Objective. This study aims to determine the diagnostic accuracy, sensitivity, and specificity of the Xpert MTB/RIF assay (Mycobacterium Tuberculosis/Rifampicin resistance) for the detection of spinal Tuberculosis (TB) and rifampicin (RIF) resistance. Summary of Background Data. The Spinal TB is often a paucibacillary extra pulmonary tuberculosis which gives a major challenge in early diagnosis and initializing the correct anti-tubercular treatment (ATT). Due to its rapidity and sensitivity, the dependence and reliability on the Xpert MTB/RIF assay has increased in the last few years. The studies describing accuracy of the Xpert MTB/RIF assay in spinal TB are scanty. Methods. This institutional review board-approved study included 360 diagnosed spinal TB patients. To determine the accuracy of the Xpert MTB/RIF assay, it was compared with other diagnostic tests like histopathology, acid fast bacilli (AFB) smear, culture, and drug sensitivity testing (DST). Results. The Xpert MTB/RIF assay showed 86.3% sensitivity and 85.3% specificity when compared with culture for the diagnosis of Spinal TB and showed 75.86% sensitivity, 96.12% specificity for RIF resistance when compared to DST. Four cases were false positive and 11 cases were false negative for RIF resistance on the Xpert MTB/RIF assay. Conclusion. The Xpert MTB/RIF assay is an efficient technique for the rapid diagnosis of spinal TB; however, a clinician should not solely rely on it for starting ATT. As there are false results also with this test which should be read cautiously and be well correlated with culture and DST pattern to guide the start of sensitive drug regimen only. The purpose is to prevent exposure of the second line drugs to false cases found on the Xpert MTB/RIF assay and avoid emergence of new acquired drug resistance.