Performance of stool Xpert MTB/RIF Ultra
A recent multicentre, prospective diagnostic study has evaluated the effectiveness of stool Xpert MTB/RIF Ultra (Ultra) in detecting Mycobacterium tuberculosis among adults living with HIV. Conducted across outpatient and inpatient health centres in Eswatini, Mozambique, and Uganda, the study enrolled 677 participants aged 15 years and older with presumptive tuberculosis.
Key Findings:
Sensitivity and Specificity: The sensitivity of stool Ultra compared to a composite microbiological reference standard (CMRS) was 23.7%, with a specificity of 94.0%. Notably, the sensitivity was higher in participants with CD4 counts less than or equal to 200 cells per μL (45.5%) compared to those with higher CD4 counts (21.3%).
Diagnostic Yield: Stool Ultra detected additional tuberculosis cases compared to sputum Ultra (23% increase), sputum culture (29% increase), and urine TB-LAM (33% increase). The overall diagnostic yield for stool Ultra was 9%, higher than sputum Ultra (6%) and sputum culture (4%), but lower than urine TB-LAM (12%).
Clinical Implications: The results suggest that stool Ultra could be a valuable additional test for tuberculosis diagnosis among people with HIV, particularly those with lower CD4 counts.
Conclusion:
The study highlights the potential of stool Ultra as a complementary diagnostic tool for tuberculosis in adults living with HIV, especially in resource-limited settings. This advancement could significantly improve tuberculosis detection and management in high-burden regions.