Imagine receiving a patient’s blood sample and being asked to test for HIV without any lab equipment, refrigeration, trained healthcare workers or electricity. A tall order, but global health non-profit PATH scientists intend to do just that, using non-instrumental nucleic acid amplification (NINA) (1), coupled with an innovative way of modulating temperature. The system has been designed to allow diagnosis of HIV and other infectious diseases in remote and isolated communities that don’t have access to laboratory services.
In low-resource locations, the lack of access to molecular testing is a significant barrier to controlling infectious disease. Transporting samples from rural communities to a central laboratory means expense, delays in getting results, and often a failure to follow up; individuals who have samples sent to a distant facility may not return to their local clinic to discover they have a disease, and therefore may not get treatment. If the lab isn’t an option, over-the-counter tests might be available, but these are antibody-based and cannot detect HIV in its early stages, when patients can be most infectious. According to the authors of a recent report, the NINA system could offer a cheap and clever alternative. The reaction is carried out in a small, portable incubator that uses the galvanic corrosion of magnesium iron alloy (only around €0.05 per reaction) when mixed with saline solution to provide heat (2). The assay, which requires a blood sample, uses reverse transcriptase-loop mediated isothermal amplification (RT-LAMP), which can be carried out at a constant temperature and does not need a thermal cycler to detect pathogen nucleic acids (in this case for HIV). Once the test is complete, the results can be visualized using a simple dipstick test, with a color band indicating the presence of disease.
Studies by the PATH scientists have shown that the incubator can maintain a stable 60°C environment at multiple ambient temperatures (see Figure 1), so testing won’t be compromised by surrounding conditions. It could also be adapted to other diseases, like malaria, and help improve the control and surveillance of multiple diseases, by allowing for advanced molecular testing to be carried out cheaply, without access to modern diagnostic equipment. To achieve this, a way of preparing nucleic acids from blood samples is also needed, as PATH senior technical officer Paul LaBarre explains: “To complete this low-resource setting diagnostic, one remaining need is the integration of a simple method for isolating nucleic acids from patient blood samples before amplification. Current methods are expensive and technically difficult. Fortunately, there are several methods we are testing that look promising.” And with detection in less than 80 minutes, the test could also become part of a point-of-care health service, with patients diagnosed and treated within a single visit – something which could be of huge benefit to underserved communities.
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References
- P. LaBarre et al., “Non-Instrumental Nucleic Acid Amplification (NINA): Instrument-Free Molecular Malaria Diagnostics for Low-resource Settings”, Conf. Proc. IEEE Eng. Med. Bio. Soc., 1087–1099 (2010). J. Singleton et al., “Electricity-Free Amplification and Detection for Molecular Point-of-Care Diagnosis of HIV-1”, PLOS ONE, 9, e113693 (2014).
