Nanoparticle capture of urinary lipoarabinomannan for diagnosing childhood tuberculosis

Urinary assays detecting lipoarabinomannan (LAM) as a diagnostic test for tuberculosis (TB) have limited sensitivity in pediatric populations. We aimed to evaluate the Ceres TB-Nanotrap to concentrate LAM and augment detection in urine using the Alere lateral flow assay (LF-LAM). This case-control study recruited 32 children with and without TB aged 1-18 years in Karachi, Pakistan, with banked urine specimens. TB case participants were classified as confirmed or unconfirmed TB using modified National Institutes of Health (NIH) consensus criteria. The LF-LAM test was performed before and after concentrating 5 mL of urine with TB-Nanotrap particles. Band intensity was measured via visual grading and digital quantification. Urine LAM sensitivity by visual grading was 4.5% (95% confidence interval [CI] 0.3-18.5) pre-concentration and 50.0% (95% CI 30.0-70.0) post-concentration. Sensitivity by digital quantification was 0.0% (95% CI 0.0-15.4) pre-concentration and 63.9% (95% CI 42.8-81.4) post-concentration. Specificity was high with both methods (visual grading: 90.0% [95% CI 62.8-99.4] pre-concentration and 90.0% [95% CI 62.8-99.4] post-concentration; digital analysis: 80.0% [95% CI 44.4-97.5] and 90.0% [95% CI 62.8-99.4], respectively). For cases, digital analysis showed an increase in median LF-LAM band intensity from 0.0 arbitrary units (AU) (interquartile range [IQR] 0.00-32.5) in unconcentrated samples to 98.4 AU (IQR 34.9-212.2) in concentrated samples. Concentration with TB-Nanotrap greatly increased sensitivity of urine LAM detection without a change in specificity. Use of TB-Nanotrap and digital quantitative analysis of urine LAM improved the diagnostic accuracy of the LF-LAM assay in this pediatric population and should be validated in larger studies.IMPORTANCEDiagnosing TB in children is challenging due to a lack of accurate and accessible diagnostic tests. In this study, we evaluated two methods of improving detection of TB in children using a commercially available urine test. First, we processed the urine to concentrate any available TB antigens. Second, we included a digital reader to interpret the test results. We found that concentrating urine and using a digital reader led to an increase in TB detection among children who had been diagnosed with TB, while minimizing false-positive results among children who did not have TB.