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Detection of Lipoarabinomannan (LAM) antigen from the urine of tuberculosis-infected children by using Ceres Nanotrap® magnetic particles
K. Ahmed1, T. Sattar1, N. T. Iqbal1,2, T. Thomas3
1 Department of Pediatrics and Child Health, Aga Khan University, Karachi, 2Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, 3 Department of Medicine, University of Virginia, USA
Background: Lipoarabinomannan (LAM) is a TB biomarker that can be detected in urine. LAM is a lipopolysaccharide antigen found in the mycobacterial cell wall and is released from metabolically active or degenerating bacterial cells. In this study, we aim to increase the sensitivity and diagnostic accuracy of one commercially available LAM test by incorporating a processing step that uses Ceres Nanotrap particles (Ceres Nanosciences, Manassas, VA, USA) to capture and concentrate LAM antigen in urine specimens from confirmed TB (GeneXpert positive) children and compare it with age-matched healthy control.
Methodology: Briefly, urine samples from the cohort of confirmed TB and HIV negative children (n=11) aged 1-18 years and their age-matched controls (n=10) from the community were tested on Alere TB LAM strips according to manufacturer’s instructions. Next, urine samples were processed using Ceres Nanotrap particles to augment the sensitivity. After following the processing steps, samples were loaded on Alere TB LAM strips. The appearance of a visible purple/gray band in the patient window was considered as positive for the presence of Mycobacteria LAM antigen in the urine sample.
Results: The positivity ratio of the LAM test were found to be increased when urine samples were processed with magnetic Ceres nanotrap particles in confirmed TB cases when compared to the unprocessed (without Nanotrap concentration) case group. When testing the original urine sample (without Nanotrap concentration), 1/11 (9%) of cases, and 1/10 (10% ) of controls had a positive TB LAM test. After processing with the Nanotrap, 6/11 (54.5%) of cases and 1/10 (10%) of controls had a positive TB LAM test. The Nanotrap increased the sensitivity of the Alere test strop from 9% to 54.5%, while maintaining the specificity at 90%.
Conclusion: Urine TB LAM assay is an attractive diagnostic biomarker test to detect TB. The approach of concentrating LAM antigen using Ceres nano trap particles enhances the algorithm of TB diagnosis and to achieve high sensitivity while minimizing false-positive results.
References:
-WHO global tuberculosis report 2019. https://www.who.int/teams/glob...