Tuberculosis diagnostic accuracy of stool Xpert MTB/RIF and urine AlereLAM in vulnerable children

Background Non-sputum-based diagnostic approaches are crucial in children at high risk of disseminated tuberculosis (TB) who cannot expectorate sputum. We evaluated the diagnostic accuracy of stool Xpert MTB/RIF and urine AlereLAM tests in this group of children. Methods Hospitalised children with presumptive TB and either age <2 years, HIV-positive or with severe malnutrition were enrolled in a diagnostic cohort. At enrolment, we attempted to collect two urine, two stool and two respiratory samples. Urine and stool were tested with AlereLAM and Xpert MTB/RIF, respectively. Respiratory samples were tested with Xpert MTB/RIF and mycobacterial culture. Both a microbiological and a composite clinical reference standard were used. Results The study analysed 219 children; median age 16.4 months, 72 (32.9%) HIV-positive and 184 (84.4%) severely malnourished. 12 (5.5%) and 58 (28.5%) children had confirmed and unconfirmed TB, respectively. Stool and urine were collected in 21,9 (100%) and 216 (98.6%) children, respectively. Against the microbiological reference standard, the sensitivity and specificity of stool Xpert MTB/RIF was 50.0% (6/12, 95% CI 21.1-78.9%) and 99.1% (198/200, 95% 96.4-99.9%), while that of urine AlereLAM was 50.0% (6/12, 95% 21.1-78.9%) and 74.6% (147/197, 95% 67.9-80.5%), respectively. Against the composite reference standard, sensitivity was reduced to 11.4% (8/70) for stool and 26.2% (17/68) for urine, with no major difference by age group (<2 and >= 2 years) or HIV status. Conclusions The Xpert MTB/RIF assay has excellent specificity on stool, but sensitivity is suboptimal. Urine AIereLAM is compromised by poor sensitivity and specificity in children.

Automated summary

This study evaluates the diagnostic accuracy of stool Xpert MTB/RIF and urine AlereLAM tests in children at high risk for disseminated tuberculosis. The results indicate that while stool Xpert MTB/RIF has excellent specificity, its sensitivity is suboptimal. Urine AlereLAM is compromised by poor sensitivity and specificity in children.