Evaluation of different diagnostic methods for spinal tuberculosis infection

Abstract

Background and purpose Tuberculosis (TB) is the most fatal infectious disease worldwide. Approximately 24.6% of tuberculosis cases are extrapulmonary and predominantly affect the spine. It is difficult to diagnose spinal TB (STB). We aimed to evaluate the diagnostic performance of the Mycobacteria Growth Indicator Tube (MGIT)-960 culture, T-SPOT.TB, Xpert Mycobacterium tuberculosis complex (MTB)/resistance to rifampin (RIF), and Metagenomic Next-Generation Sequencing (mNGS) to detect STB. Methods We assessed 126 patients presumed to have STB using these four methods. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using clinical diagnosis as a reference. Results Of the patients, 41 were diagnosed with STB and 85 with non-STB. In the STB group, the sensitivity, specificity, PPV, and NPV of the MGIT-960 culture were 29.3% (12/41), 100% (85/85), 100% (12/12), and 74.6% (85/114), respectively. The sensitivity, specificity, PPV, and NPV of T-SPOT.TB were 92.7% (38/41), 82.4% (70/85), 58.5% (31/53), and 95.9% (70/73), respectively. The sensitivity, specificity, PPV, and NPV of the Xpert MTB/RIF assay were 53.7% (22/41), 100% (85/85), 100% (22/22), and 81.7% (85/104), respectively. The sensitivity, specificity, PPV, and NPV of mNGS were 39.0% (16/41), 98.8% (84/85), 94.1% (16/17), and 77.1% (84/109), respectively. The sensitivity, specificity, PPV, and NPV of mNGS + Xpert MTB/RIF were 73.2% (30/41), 100% (85/85), 96.8% (30/31), and 72.0% (85/118), respectively. The sensitivity, specificity, PPV, and NPV of the mNGS + T-spot assay were 97.6% (40/41), 100% (85/85), 67.9% (38/56), and 75.9% (85/113), respectively. Moreover, the sensitivity, specificity, PPV, and NPV of T-spot + Xpert MTB/RIF were 95.1% (39/41), 100% (85/85), 72.2% (39/54), and 81.0% (85/105), respectively. Conclusions T-SPOT.TB is the most effective method for diagnosing STB; however, Xpert MTB/RIF is more reliable and can detect RIF resistance. Clinicians can use mNGS to identify pathogens in patients with spinal infections; these pathogens appeared to be more meaningful in guiding the clinical management of patients in the non-STB group. The combination of Xpert MTB/RIF and mNGS can improve the early diagnosis rate and drug resistance detection, reduce the diagnostic cycle, and provide early targeted anti-TB treatment for patients with STB.

First whole genome sequencing data of a Mycobacterium tuberculosis STB-T1A strain isolated from a spinal tuberculosis patient in Sabah, Malaysia

“…The sample was subjected to tuberculosis (TB) detection with Xpert Ⓡ MTB/RIF Ultra (Cepheid, Sunnyvale, CA, USA) following the manufacturer's protocol. The processed sample was transferred to a cartridge and inserted into a GeneXpert machine for automated DNA extraction and real-time polymerase chain reaction (qPCR) for qualitative detection of Mycobacterium tuberculosis Complex (MTBC) and rifampicin (RIF) resistance [2] . Based on the cycle threshold (Ct) value, the semi-quantitative bacterial load was reported.…”

“…The processed sample was cultured in a Mycobacterium Growth Indicator Tube (MGIT) tube containing 7H9 Middlebrook broth with PANTA (polymyxin-B, Amphotericin-B, nalidixic acid, trimethoprim, azilocillin) antibiotic and OADC (oleic acid, albumin, dextrose, catalase) supplement mixture. The tube was loaded into the BD BACTEC™ MGIT™ 320 system (Becton, Dickinson, NJ, USA), and incubated at 37 °C until bacterial growth was detected by the system [2] . DNA was extracted using the Masterpure™ Complete DNA and RNA Purification kit (Epicentre Biotechnologies, Madison, WI, USA) according to the manufacturer's instruction, with an extended lysis protocol for 16 h with Proteinase K. The quality of the extracted DNA was determined by Nanodrop 2000c spectrophotometer (ThermoFisher Scientific, USA) and gel electrophoresis [3] .…”