APPLICATION OF XPERT MTB/RIF IN RIFAMPICIN RESISTANCE DETECTION AND DIAGNOSIS OF SPINAL TUBERCULOSIS

Peng Wu¹, Li Luo², Zhen Chen^{1, *}

¹Department of orthopedics, General Hospital of Ningxia Medical University, Yinchuan, China - ²Department of neonatal, General Hospital of Ningxia Medical University, Yinchuan, China

Introduction: To explore the application of Xpert MTB/RIF in the detection of rifampicin resistance and the diagnosis of spinal tuberculosis.

Materials and methods: This study collected 146 patients with suspected spinal tuberculosis who were treated by spinal surgery in our hospital from December 2019 to December 2021, and the lesion tissue (pus, caseous tissue, granulation) in the operation area was collected from each patient. The lesion tissue (pus, caseous tissue, and granulation tissue) in the operation area was collected from each patient and divided into two parts, one for histopathological examination, the other for tuberculosis smear, tuberculosis culture, and GeneXpert detection. Rifampicin Drug Sensitive Test (DST) was performed in patients with positive Mycobacterium tuberculosis culture. The efficacy of Xpert MTB/RIF to detect rifampicin resistance was analyzed, and the sensitivity and specificity of Xpert MTB/RIF to detect Mycobacterium tuberculosis was calculated. Moreover, the differences with acid-fast staining, sensitivity, and specificity of rapid culture of Mycobacterium tuberculosis were compared. The Composite reference standard (CRS) was used as the diagnostic standard in this study to evaluate the diagnostic performance of Xpert MTB/RIF for detecting spinal tuberculosis. CRS include: Mycobacterium tuberculosis smear, Mycobacterium tuberculosis culture, clinical manifestations, histopathology, computed tomography (CT) and Magnetic Resonance Imaging (MRI), and follow-up for 3 months after enrollment. Under CRS diagnostic criteria, patients were divided into 4 groups: confirmed spinal tuberculosis group, clinically diagnosed spinal tuberculosis group, suspected spinal tuberculosis group, and non-spinal tuberculosis group.

Results: In this study, 146 patients were collected, 9 were excluded, and 137 patients were finally included. There were 75 males and 62 females, with an average age of 44.28±16.98 years. There were 14 cases of cervical vertebrae, 37 cases of thoracic vertebrae1-9, 50 cases of thoracolumbar segment, and 36 cases of lumbar vertebrae3-5. Taking CRS standard as reference, 123 of 137 patients were diagnosed as spinal tuberculosis. Among them, there were 68 cases in the confirmed spinal tuberculosis group, 31 cases in the clinically diagnosed spinal tuberculosis group, 24 cases in the suspected spinal tuberculosis group and 14 cases in the non-spinal tuberculosis group. The sensitivity of Xpert, smear and culture were 82.93% (102/123), 29.27% (36/ 23) and 48.36% (59/122) respectively. The sensitivity of Xpert, smear and culture were statistically significant (P<0.05). The specificity of Xpert, smear and culture were 100% (14/14) and 100% (14/14) respectively 93.33% (14/15). DST were performed on 59 specimens with positive culture, of which 12 were rifampicin-resistant and 47 were rifampicin-sensitive. Among the 12 cases of rifampicin resistance diagnosed by DST, 11 cases were rifampicin resistance diagnosed by Xpert and 1 case was rifampicin sensitive diagnosed by Xpert. Among the 47 rifampicin-sensitive cases diagnosed by DST, 3 were rifampicin-resistant and 43 were rifampicin-sensitive by Xpert. The sensitivity of Xpert to detect rifampicin resistance was 91.67% (11/12), the specificity was 93.62% (44/47).

Conclusions: Xpert MTB/RIF is a molecular detection technology that can simultaneously detect the resistance of Mycobacterium tuberculosis and rifampicin to spinal tuberculosis, which has high diagnostic value in the rapid diagnosis of spinal tuberculosis.