BOSTON — An experimental urine-based assay can accurately detect Zika virus in less than 20 minutes, according to findings presented here at the American Urological Association 2017 Annual Meeting.
There is an urgent need for a rapid assay because current testing can take 2 to 4 weeks, said researcher Laura Lamb, PhD, from Beaumont Health and the Oakland University William Beaumont School of Medicine in Auburn Hills, Michigan, who is one of the developers of the test.
"Our goal was to come up with a fast, accurate, and reliable test that is affordable and would be done at the point of care, so you would know your result before you left the doctor's office," she explained. "The real goal is prevention, so couples planning to conceive can understand their status and plan accordingly."
Because Zika infections are generally mild or asymptomatic, adults often are unaware that they have been affected. Although the primary source of infection is mosquitoes from the Aedes genus, the virus can also be sexually transmitted, which is why at-risk men and women who are planning to conceive should be tested.
The consequences of infection can be severe. "One in 10 women infected with Zika during pregnancy will have a child with a severe life-long birth defect, such as microcephaly, and there are many other birth defects we are just starting to understand," Dr Lamb explained.
Molecular tests, such as the Trioplex rRT-PCR real-time polymerase chain reaction for urine, blood, and/or saliva samples, are currently available, as are serologic tests, such as the Zika MAC-ELISA IgM antibody-capture enzyme-linked immunosorbent assay.
The new rapid assay uses loop-mediated isothermal amplification to detect viral RNA or DNA for the three strains of Zika most prevalent in North and South America.
Zika can be found in urine 2 to 20 days after exposure, whereas it can only be detected in blood 1 to 11 days after, and in saliva 1 to 8 days after, according to a study conducted by the Florida Department of Public Health (MMWR Morb Mortal Wkly Rep. 2016;65:475-478).
New Assay Specific and Sensitive for Zika
For their study, Dr Lamb and her colleagues used isothermal amplification and RT-PCR to test urine samples infused with Zika virus and related arboviruses, such as Dengue fever.
The test was highly specific for the detection of Zika but not other viruses in the samples. It was also sensitive for Zika, detecting viral DNA at levels of a few hundred copies per milliliter, which the researchers hope to reduce, and detecting the virus in the remains of a single mosquito.
Isothermal amplification is faster and more specific than RT-PCR, and does not require trained personnel to read the results. Plus, it can be performed with a heating pack, similar to the ones used by American troops to heat food packages in the field, whereas RT-PCR requires a thermal cycler.
If the commercial version of the assay is approved, it will likely be fairly inexpensive. Isothermal amplification tests currently used in the agriculture industry cost just a few dollars.
A Clinically Relevant Issue
"Last week, I counseled three couples who had recently traveled to endemic areas and are holding off on their first reproduction for at least 6 months, so this is a very relevant issue," said session moderator Robert Brannigan, MD, a urologist from the Northwestern Medical Group in Chicago.
The incorporation of the urine test into clinical practice would depend on cost, availability, sensitivity, and specificity, he told Medscape Medical News. "But from everything I've heard, for people who have recently traveled to an endemic area who raise this issue, it is something I would offer."
The assay appears to be "a huge breakthrough," said Gennady Bratslavsky, MD, professor and chair of urology at the SUNY Upstate Medical University in Syracuse, New York.
"However, at this point, the researchers have only tested for the known, documented cases of Zika virus," he cautioned. "There are numerous strains of Zika virus that exist, or may exist, and they show numerous mutations as viruses adapt to the environment."
To be truly effective, the test would have to include primers directed against genetic sequences in the virus that have been conserved through evolution and are presumably necessary for its ability to survive and replicate, Dr Bratslavsky explained.
And there have been reports of men with evidence of the Zika virus in semen but not in blood or urine, Dr Brannigan pointed out, which could be missed with a urine-based test.
The assay development is supported, in part, by the Maureen and Ronald Hirsch family philanthropic fund. Dr Lamb and her codevelopers hold a patent on the assay. Dr Brannigan and Dr Bratslavsky have disclosed no relevant financial relationships.
American Urological Association (AUA) 2017 Annual Meeting: Abstract MP23-03. Presented May 13, 2017.
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Cite this: Zika Virus Detected Quickly in Urine With Experimental Test - Medscape - May 17, 2017.
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