Higher sensitivity of Xpert MTB/RIF Ultra over TB culture for the diagnosis of spinal tuberculosis using open or CT-guided biopsies
Robyn Waters, Maritz Laubscher, Robert N Dunn, Nawaal Adikary, Anna K Coussens, Michael Held- Infectious Diseases
- Oncology
Abstract
Background
Diagnostic specimens for spinal tuberculosis (STB) are mostly collected via open surgery. Percutaneous CT-guided biopsies are used in times of limited surgical availability. However, poor diagnostic accuracy of Mycobacterium tuberculosis (Mtb) culture has been reported using this method, due to limited sample volume and the paucibacillary nature of STB. We evaluated Xpert MTB/RIF Ultra on open and CT-guided biopsies compared to gold standard Mtb culture and histopathology.
Methods
We conducted a prospective diagnostic accuracy study of Xpert Ultra, compared to TB culture and histopathology, in adults with signs and symptoms of STB at a tertiary academic hospital in South Africa, between November 2020 to December 2021. Diagnostic testing was performed on 31 patients with available samples.
Results
Xpert Ultra had a sensitivity of 94.7% (95% CI: 75.3-99.7) and specificity of 100% (95% CI: 75.7 - 100.0) against a reference standard of Mtb culture and histopathology. Xpert Ultra had high diagnostic accuracy in both open and CT-guided biopsy samples (sensitivity/specificity for open and CT-guided: 100%/100% and 89%/100%, respectively). Mtb culture had limited specificity for CT-guided biopsies (43%; 95% CI: 15.8-74.9). HIV-1 co-infection did not impact Mtb abundance measures by Xpert Ultra or culture. Xpert Ultra was also superior to culture for STB diagnosis in patients concurrently treated for pulmonary TB.
Conclusion
Xpert Ultra detected more STB cases than culture for CT-guided biopsy samples, and no difference in sensitivity for open biopsies, irrespective of HIV-1 status, making it an important tool for rapid diagnosis especially during times or in locations where open surgery is not possible or concurrent pulmonary TB treatment is initiated.