Testing failures have weighed down the US Covid-19 response since the virus emerged. More than half a year in, many labs are overwhelmed, leading to long waits for results and robbing individuals and public health officials of crucial information.
No single breakthrough will solve the problem. But a series of small ones promise to help. One of these is a new, cheap saliva test called SalivaDirect, developed by researchers at a Yale laboratory, partially funded by the National Basketball Association and just approved for use by the Food and Drug Administration. Rather than sell kits or test samples on their own, the researchers are sharing their method with local labs for free.
By taking up this technique and expanding its use, labs nationwide can help the country dig out of its testing hole.
The new test differs from the swab-based PCR (polymerase chain reaction) tests that are the most used in the US. PCR tests are highly accurate and are designed to run at high volume on broadly available machines. But processing them takes specialized equipment, manpower and time.
The swabs that health workers use to collect genetic samples need to be transported in specialized tubes containing a custom medium. Once at the lab, a specific reagent (not always easy to procure) must be used to extract RNA.
The Yale researchers wanted to find a simpler process that would be easier on patients. As Anne Wyllie, one of those researchers, said, “Who actually enjoys a nasopharyngeal swab?”
The lab was able to detect coronavirus in saliva, and then searched for a way to put samples directly into testing machines, without using reagents. After working on the problem for a few months, the researchers assembled a test that requires nothing but spit in a tube, the application of heat, and a widely available chemical reagent.
The group estimates that the reagent cost per sample ranges from $1.29 to $4.37, which is far cheaper than the reagents used in current PCR tests. The lab is granting licenses only to other laboratories that agree to charge an affordable price for the test.
SalivaDirect still relies on the core laboratory technology and machines that are now overwhelmed by Covid-19 tests. But by bringing more labs into the effort, it could help ease the backlog.
Even so, the new test can be only part of the solution. Other fast tests that can be run outside of labs are also needed. But Wyllie hopes the FDA’s approval of SalivaDirect will lead to many more tests getting a green light. “We’ve broken a couple of regulatory hurdles that have been barriers against methods that we could use for screening and surveillance rather than diagnostic testing,” she says.
When testing capacity is short, states and labs have to focus efforts on confirming that people are sick, rather than test broadly to catch and isolate potential spreaders. New options like SalivaDirect that reduce costs and difficulty enable frequent and repeated testing, which can stop potential outbreaks early.
The NBA is using easy daily tests, some from SalivaDirect, to run a large basketball tournament in mid-outbreak Florida. Extending that approach would result in fewer foreseeable disasters, such as the University of North Carolina’s failed effort to bring students back to campus without a robust testing plan.
Before it can hope to do routine screening, the US needs to get to a point where it can turn around high-priority tests in a reasonable time (less than two days).
SalivaDirect is an important step toward both short-term capacity building and a brighter testing future.
Bloomberg
