A point-of-care device for the rapid diagnosis of tuberculosis

  • Wong S
  • Drain P
  • Klapperich C
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Abstract

Program/Project Purpose: Despite being a largely curable disease, tuberculosis infected 8.6 million people and killed 1.3 million in 2012. These grim statistics are largely due to low detection rates- approximately 60% of suspected TB cases go undiagnosed and untreated because there is no fast and accurate way to detect TB. We aim to develop a simple-to-use, inexpensive, and rapid point-of-care TB diagnostic for use in low-resource settings where TB is most prevalent. Structure/Method/Design: For years, TB diagnostics has remained surprisingly stagnant. Recently, a new option became commercially available: a lateral flow assay that functions like a home pregnancy test. The test-DetermineTM TB LAM Ag test (Alere Inc.)-diagnoses TB by detecting lipoarabinomannan (LAM), a cell wall glycolipid of Mycobacterium tuberculosis that is shed into the urine of persons with active TB. Although initially promising, numerous clinical evaluations have convincingly demonstrated that the test's sensitivity is too low to accurately diagnose the general TB population. The problem is likely that urinary LAM concentrations are naturally present at levels too low to be immunodetectable. Some studies, however, suggest that a 10-fold increase in LAM concentration could dramatically improve its immunodetectability. We developed a method to pre-concentrate LAM without sophisticated laboratory equipment (e.g., centrifuge) to enhance its downstream immunodetection. Our technology can be easily translated to a battery-powered, point-of-care platform and readily integrated with a test like DetermineTM to leverage the diagnostic's simplicity and commercial availability. To pre-concentrate LAM, we applied localized heat to a paper-based device to enhance urine evaporation and LAM concentration. We proved the feasibility of this strategy by concentrating bromophenol blue (BPB) in water and LAM in water or urine using a commercial resistive heater (as the localized heat source) heated to 220degreeC with a benchtop power supply. BPB and LAM were quantified via spectrophotometry and immunoblotting, respectively. Outcomes & Evaluation: Initial tests to concentrate BPB in water by heating the paper strip for 10 minutes resulted in a 19-fold concentration of BPB (19.2 +/- 3.5; n=3). Concentrating LAM in water for 10 minutes resulted in a 21-fold increase in LAM (21.4 +/- 1.5; n=3). The comparable degree of concentration of BPB and LAM in water suggests that the application of heat did not compromise the subsequent immunodetectability of LAM. Concentrating LAM in urine for 20 minutes required 500mW of power and resulted in an 18-fold enhancement in immunodetectability (17.9 +/- 4.9; n=3). Given the low power requirement, our technology can be readily adaptable to a battery-powered platform. Going Forward: The next step is to field test our pre-concentration technology using clinical samples obtained from a cohort of TBinfected individuals from South Africa. We are also currently translating our technology onto a battery-powered platform.

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Wong, S., Drain, P. K., & Klapperich, C. (2015). A point-of-care device for the rapid diagnosis of tuberculosis. Annals of Global Health, 81(1), 85. https://doi.org/10.1016/j.aogh.2015.02.700

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