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 a urine processing step using the Ceres TB-Nanotrap to concentrate available LAM antigens and augment LAM detection in urine using the Alere lateral flow assay (LF LAM). This case-control study recruited children with TB and non TB controls aged 1 to 18 years from outpatient clinics. The LF LAM test was performed before and after concentrating 5mL of urine with 400uL of magnetic 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% [62.8 - 99.4] pre concentration, 90.0% [62.8 - 99.4] post concentration; digital analysis 80.0% [44.4 - 97.5], 90.0% [62.8 - 99.4] respectively). For cases, digital analysis showed an increase in median LF-LAM band intensity from 0.0 arbitrary units (AU) (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 change in specificity. Digital quantitative analysis further increased sensitivity. 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.