Drug sensitivity patterns in Xpert-positive spinal tuberculosis: an observational study of 252 patients.

PURPOSE: To evaluate the sensitivity patterns of anti-tubercular drugs in Xpert MTB-positive spinal tuberculosis (TB) patients and to formulate the guidelines for early start of empiric anti-tubercular treatment (ATT) in MDR-TB spine based on resistance pattern in this large series. METHODS: It was a cross-sectional observational study of 252 consecutive patients who were Xpert MTB-proven spinal TB cases with retrospective analysis of prospective data. The Xpert MTB/RIF (Mycobacterium tuberculosis/rifampicin) assay was used to diagnose spinal TB and RIF resistance. All patients underwent drug sensitivity testing (DST) to 13 commonly used anti-tubercular drugs using BACTEC MGIT-960 system. The drug sensitivity pattern of primary and secondary anti-tubercular drugs was recorded and compared. RESULTS: The DST study revealed 110 (43.6%) cases of multi-drug resistant (MDR-resistance to both isoniazid and rifampicin) and 24 (9.5%) cases of non-MDR-TB spine. The widespread resistance was found for both isoniazid (91%) and rifampicin (85%), followed by streptomycin (61.9%). The least resistance was found for kanamycin, amikacin and capreomycin and no resistance found for clofazimine. CONCLUSION: The Xpert MTB/RIF assay is an efficient technique for the rapid diagnosis of spinal TB and suspected MDR-TB; however, it is recommended to do culture and DST in all patients with spinal TB to guide the selection of appropriate second-line drugs when required. In cases of non-availability of culture and DST, it is suggested to use data from large series such as this to plan the best empirical ATT regimen. These slides can be retrieved under Electronic Supplementary Material.

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. LEVEL OF EVIDENCE: 4.