Using 3D printing and a chemical heat source, University of Pennsylvania researchers have created a proof-of-concept for an affordable Zika test that returns results in just 40 minutes
There’s a gap in Zika virus testing that researchers at the University of Pennsylvania hope to fill. That gap is a point-of-care test for the Zika virus that can produce a fast and accurate result, whether in developed nations or in developing countries that don’t have many state-of-the art clinical laboratories.
Although numerous Zika virus tests have earned Emergency Use Authorizations from the US Food and Drug Administration (FDA), gold standard detection is still limited to medical laboratories. To date, the FDA’s list of current and terminated Emergency Use Authorizations include no point-of-care options to help medical professionals quickly screen patients for Zika infection.
As noted by the Center for Disease Control and Prevention’s “Interim Guidance for Interpretation of Zika Antibody Test Results,” the antibodies that indicate Zika virus activity also share similarities with other flavivirus viruses. Of particular note is similarities with Dengue virus—a virus prevalent in many of the areas in which Zika is found.
In coverage of a new test in proof-of-concept at University of Pennsylvania School of Engineering and Applied Science by Phys.org, Research Assistant Professor Changchun Liu, PhD, highlighted this concern, saying, “Generally, lateral flow tests, which directly change the color of a test strip based on the presence of Zika antibodies, suffer from low sensitivity. And since antibodies to the Zika virus cross-react with other similar viruses prevalent in Zika-endemic areas, lateral flow tests for Zika also suffer from low specificity.”
Current Zika Tests Require Clinical Laboratories for Sensitivity and Specificity
While tests, such as lateral flow paper tests, can use antibodies to detect Zika infection, antibody similarities increase the risk of a false positive, or of treating the wrong virus. Dependence on reaching certain antibody thresholds also increases the risk of false negatives and hampers the ability for antibody-based tests to offer early detection benefits.
Due to this lack of sensitivity and specificity, current gold standard tests detect genetic material from the Zika virus itself instead of antibodies. However, doing so requires the use of reverse transcriptase polymerase chain reaction (RT-PCR). This process requires both a skilled lab professional and the ability to precisely adjust temperatures at key stages of the testing process.
Engineers at University of Pennsylvania have develop a highly sensitive reverse-transcription loop-mediated, isothermal amplification (RT-LAMP) assay (above) for rapid detection of the Zika Virus. The test includes a simple, easy-to-use, inexpensive, point-of-care (POC) disposable cassette that carries out all the unit operations from sample introduction to detection. The system, according to the engineers, is particularly suitable for resource-poor settings, where centralized laboratory facilities, funds, and trained personnel are in short supply, and for use in doctors’ offices, clinics, and at home. (Image and caption copyright: University of Pennsylvania.)
Engineers at University of Pennsylvania hope to solve this problem by using a low-cost, 3D printed processor that mimics an insulated thermos bottle. Instead of amplifying RNA through RT-PCR, the team uses reverse transcription loop-mediated isothermal amplification (RT-LAMP). This eliminates the need for precise temperature cycling and allows the processor to work using a chemical-based heat source. They hope their latest proof-of-concept will offer the speed and ease-of-use of a lateral flow test while improving specificity and sensitivity to levels comparable to current gold standard RT-PCR tests.
No Medical Laboratory Needed with New Zika Test
In a study published in Analytical Chemistry, the engineers explained their system, stating, “We engineered a low-cost, point-of-care system that consists of a diagnostic cassette and a processor. The cassette isolates, concentrates, and purifies nucleic acids, and carries out enzymatic amplification. The test results are indicated by the change in the color of a dye, which can be inspected visually.”
These traits make it possible to both process samples and obtain a diagnosis without a traditional medical laboratory. Use of a chemical heat source means there is no need for electricity. This makes the proof-of-concept an ideal candidate for use in remote regions or developing areas without access to modern medical facilities. Better still, the lateral flow test’s visual indicator eliminates the need for extensive operational training or skilled analysis. After gathering a sample, the test completes in approximately 40 minutes.
However, the test still requires further validation. In the study, researcher Professor Haim H. Bau, PhD, noted, “Before the assay can be adapted for medical use, we must experiment with patients’ samples and [ensure] that our assay and system match the performance of the gold standard and operate reproducibly and reliably.”
Low-Cost Test Also a Home-based Option for Detecting Zika
Even in areas with modern clinical laboratories and healthcare, the test might help to improve access to testing due to its low cost. As reported by NBC News, the cost of the first commercial US test cleared for emergency use in diagnosing Zika virus was $500 at the time of publication. In comparison, the test engineered at University of Pennsylvania is estimated to cost approximately $2. Should it prove accurate and reliable, it also offers potential of a home-based detection option for those who cannot make it to a medical facility or prefer to test in private.
This proof-of-concept highlights how, through the clever use of technology and innovative thinking, new tests can continue to lower testing costs associated with pathology while also reducing the time required to form a diagnosis—all without sacrificing sensitivity or specificity.
—Jon Stone
Related Information:
Portable Test Rapidly Detects Zika in Saliva for $2 (Update)
Instrument-Free Point-of-Care Molecular Detection of Zika Virus
First Commercial Zika Virus Test Gets FDA Approval
Interim Guidance for Interpretation of Zika Virus Antibody Test Results
