Performance of stool Xpert MTB/RIF Ultra for detection of Mycobacterium tuberculosis among adults living with HIV: a multicentre, prospective diagnostic study.

Summary

In 677 adults with HIV across three African countries, stool Xpert Ultra showed overall sensitivity of 23.7% and specificity of 94.0% versus a composite reference; sensitivity rose to 45.5% when CD4 ≤200 cells/μL. Stool Ultra added 23–33% extra cases compared with sputum Ultra, sputum culture, or urine TB-LAM, supporting its role as an adjunct diagnostic in PLHIV.

Key Findings

• Overall stool Ultra sensitivity 23.7% (95% CI 16.4–32.4) and specificity 94.0% (95% CI 91.7–95.9) versus composite reference.
• Higher sensitivity in advanced immunosuppression: 45.5% with CD4 ≤200 cells/μL vs 21.3% with CD4 >200.
• Stool Ultra added 23–33% additional cases compared with sputum Ultra, sputum culture, and urine TB-LAM across all tested.
• Diagnostic yield among all treated: stool Ultra 9%, urine TB-LAM 12%, sputum Ultra 6%, sputum culture 4%.

Clinical Implications

Incorporate stool Xpert Ultra as an adjunct test in TB diagnostic algorithms for PLHIV—prioritizing those with CD4 ≤200 cells/μL—and combine with urine LAM and sputum testing to maximize yield.

Limitations

• Overall sensitivity was modest; performance may vary with stool processing and bacillary load.
• Study population limited to adults with HIV; generalizability to HIV-negative populations not assessed.

Future Directions

Optimize stool processing workflows and evaluate integration with triage tools (e.g., clinical scores, digital CXR) in implementation studies; assess cost-effectiveness and impact on time-to-treatment.