Paper (ELISA) Plates

Human immunodeficiency virus (HIV) is one of the leading causes of death worldwide, especially in rural countries, and it’s estimated that up to one-third of HIV-positive individuals are co-infected with hepatitis C (HCV), which unsurprisingly affects their care needs and survival rates. Because existing tests either require fully equipped clinical laboratories or lack accuracy, it’s difficult to identify these patients in rural or resource-limited settings. Xinyu Liu, part of a group developing a portable, low-cost HIV/HCV testing platform, is tackling the challenge.

What inspired you to develop a low-cost platform for HIV and HCV testing? 

This project was initiated through a Star in Global Health Award granted by Grand Challenge Canada. Our goal was to develop a low-cost diagnostic platform for use in African countries where sexually transmitted infections (STIs) like HIV and HCV are major life-threatening diseases. Although rapid point-of-care tests (POCT) for HIV/HCV have been used in the past, we still very much need new diagnostic platforms that are affordable, but don’t compromise on high accuracy, sensitivity and throughput.

The ideal setting for use of the platform is in small clinics in remote or resource-poor settings with limited access to laboratory services, such as clinics in developing countries like Kenya, or community clinics in rural and northern Canada. It’s also useful for the care of elderly or disabled patients whose conditions need to be monitored at home.

How does your paper-based test work?

The platform includes a paper device with eight disposable electrochemical biosensors and a custom-made, low-cost, handheld potentiostat (an electrochemical reader). It allows users to carry out eight simultaneous ELISAs – four for HIV and four for HCV antibodies – providing a higher throughput than existing HIV/HCV POCTs. To run a test, you simply insert the paper device into the potentiostat, add microliter drops of serum sample and reagents to the eight biosensors, and trigger the electrochemical measurement by pressing a button on the potentiostat. The results can be displayed on the potentiostat’s LCD screen, or transmitted to a smartphone, computer or remote site for telediagnosis or healthcare data collection (Figure 1).

What sets the new device apart from previous testing methods?

Our technology puts ELISA, one of the most commonly performed clinical tests, on a highly portable and inexpensive platform. It requires no laboratory infrastructure, very low-level operator skills, completes eight tests in parallel within 20 minutes, and provides quantitative results with comparable accuracy, sensitivity and specificity to clinical analyzers. It can also telecommunicate, making it compatible with existing e-health systems. The paper-based device only takes three microliters of serum sample per test, so the blood from a fingerprick should be enough to perform the diagnostics.

Our platform is still a laboratory prototype, though, and requires further development. It can’t handle whole blood samples at this point, so blood drawing and separation are still needed. We’re working to incorporate a membrane into the device for on-chip plasma separation. This will allow the test to be run directly from a fingerpick sample. Also, although our laboratory calibration experiments have demonstrated satisfactory performance, we still need to conduct a systematic evaluation of our device against gold-standard ELISA using patient blood samples to further verify its clinical performance.

How might it change the day-to-day work of those involved in HIV and HCV testing?

The platform was designed not to replace conventional molecular diagnostic tests routinely performed in well-equipped laboratories, but to provide a low-cost and easy-to-operate alternative for use elsewhere. It allows rapid and accurate HIV/HCV testing by less skilled operators at the point of care, and could facilitate the day-to-day work of pathologists and laboratory professionals who need to perform HIV/HCV tests outside laboratory environments.

The technology isn’t only applicable to HIV/HCV, but to many molecular diagnostic tests. ELISAs are widely used in clinical laboratories to detect various antigen and antibody disease markers, so our test could be adapted to diagnose any disease using such a biomarker. For instance, we’re currently pursuing testing for cardiovascular diseases and cervical cancer. In the future, the platform could also be used for nucleic acid tests, also widely used in diagnostics.

But first, we need to ready the platform for clinical use by performing real patient sample testing in Canada and Kenya, and by further developing the engineering aspects of the platform for technology transfer. We expect to achieve initial adoption of a commercial version of the device in Kenyan clinics within five years, but its adoption in western countries – where market barriers and regulatory processes are more complex – will take longer.