The quest for fast, accurate and cheap diagnostic tools for the Zika virus has been underway since the infection first took hold in South America last year. Researchers from the Philadelphia-based University of Pennsylvania have created a portable test that relies on color-changing dyes to notify users when viral RNA that matches Zika's is present in a sample. It's about the size of a soda can and costs just $2.
Diagnostic tools that detect genetic material from Zika itself, rather than from antibodies that could produce false negatives or positives, are considered a gold standard, according to the researchers. The main hurdle to the kind of test developed at UPenn is amplification, a process in which temperature changes enable the patient sample to be copied enough times that the presence of viral RNA can be detected. The researchers overcame this challenge by using an alternative technique in which the sample can be amplified while maintaining a stable temperature, according to Changchun Liu, PhD.
"The CDC has approved, on an emergency basis, only these kinds of laboratory-based molecular tests for the Zika virus," Dr. Liu said in a statement. "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."
After saliva is introduced into the device, results are returned in under an hour, and researchers are testing future versions of the device that will use an integrated smartphone camera to detect viral load using fluorescent dye. Their findings are published in Analytical Chemistry.
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