New COVID testing technique might velocity up backlogged labs
Samples scraped from the again of sufferers’ noses and throats can now be bundled collectively and examined for the coronavirus in teams in one of many nation’s greatest business labs. Quest Diagnostics, which handles tens of hundreds of coronavirus assessments every day, acquired authorization for the tactic, known as pooled testing, from the Meals and Drug Administration over the weekend.
The technique helps preserve sources by working a number of assessments utilizing the supplies often required for one. It might additionally assist Quest keep away from backlogs and transfer testing alongside extra rapidly. Proper now, demand for testing is so excessive that it takes a median of seven days for Quest labs to get outcomes to sufferers.
Nevertheless, the technique can’t clear all testing roadblocks, and it might not work as nicely within the areas the place it’s most wanted: outbreak hotspots, the place testing sources are stretched the thinnest. In these environments, the place a excessive share of assessments change into optimistic, swimming pools don’t find yourself saving supplies — too many are optimistic, which suggests extra retesting.
“When the positivity fee is excessive, pooling isn’t very efficient, since you’re splitting aside method too many swimming pools, and it’s simply not price your effort,” says Peter Iwen, director of the Nebraska Public Well being Laboratory.
Quest’s methodology will mix samples taken from 4 individuals. If the multi-sample check is destructive, all 4 are thought of destructive. If it’s optimistic, every pattern will get retested by itself to determine who has the virus. The corporate mentioned in a press launch that it’s going to begin rolling out pooled testing at its labs in Chantilly, Virginia, and Marlborough, Massachusetts, by the tip of the week, earlier than increasing to different areas. Quest didn’t reply to a request for remark.
Consultants have been concerned about pooled testing for months. The strategy is already generally used to display screen individuals for sexually transmitted infections, and it’s used to test for ailments in donated blood as nicely. Deborah Brix, a member of the White Home coronavirus activity pressure, advised an American Society for Microbiology convention final month that the technique might dramatically improve the variety of assessments finished within the US every day.
Again in March, Iwen began exploring pooled assessments within the Nebraska Public Well being Lab. He was working low on the chemical substances wanted to run every check and knew that he might preserve them by grouping samples collectively. He ran some experiments and located that he might do it efficiently. “It really works nice, and I can save anyplace from 60 to 70 p.c of our reagents,” he says. He obtained approval to maneuver ahead from Nebraska’s governor beneath their state of emergency.
“We began pooling, and we have been capable of hold the lab working,” Iwen says.
Shortages of testing supplies is simply the kind of roadblock a pooled testing technique may help overcome, says Nikhil Gopalkrishnan, a postdoctoral fellow at Harvard’s Wyss Institute for Biologically Impressed Engineering. However provide shortages aren’t the one situation holding up testing. “Relying on what the precise downside is, pooling could make an actual influence, or it couldn’t,” he says. “If it seems that they’re quick staffed, they usually simply don’t have sufficient individuals, and the limiting issue is that somebody has to unscrew all of the tubes — pooling isn’t going that can assist you there.”
Pooling additionally doesn’t assist as soon as the speed of infections in a neighborhood begins ticking up. Iwen needed to cease utilizing pooled testing within the Nebraska lab just a few weeks again as a result of the share of assessments that got here again optimistic was too excessive — above 10 p.c. In any random group of 4 or 5 assessments, there was a excessive likelihood that one could be optimistic. If the optimistic fee is that prime, pooling doesn’t have a tendency to avoid wasting a major quantity of chemical substances or time.
The brand new directions for the Quest pooled testing say that, if 13 p.c of assessments finished at a lab are coming again optimistic, the lab ought to drop the pool dimension down to 3. If 25 p.c of a lab’s assessments are coming again optimistic, they shouldn’t do pooled testing. Virginia and Massachusetts, house to the primary Quest labs set to make use of pooled testing, positivity fee is about 6 and a couple of p.c, respectively. In Arizona, one of many hardest-hit states, it’s round 24 p.c.
It’s potential to make pooled testing work in an space with a excessive share of optimistic assessments, Iwen says. If they’ve details about sufferers (if they’ve signs, the place they reside, the place they work), they’ll classify them as excessive or low threat. “You may pool those that you simply suppose are thought of low threat. You may try this in anywhere, even when their general fee could be very, very excessive,” he says.
That solely works if labs can get good demographic info on the samples they’re testing. However usually, labs get samples and do not know the place they got here from, Iwen says.
Regardless of the restrictions, Gopalkrishnan says that the Quest authorization is an effective first step towards extra widespread pooled testing. He’d wish to see larger pool sizes, notably in areas the place there isn’t a lot unfold of COVID-19. Bumping swimming pools as much as tens of samples, or as excessive as 100, might assist labs transfer by way of samples much more rapidly. “I believe you’ll see extra pooling authorizations are available,” he says.
Iwen thinks that implementing pooled testing correctly may help testing transfer extra rapidly. “It is a course of that must be thought of if we’re going to do the testing that’s been requested of the laboratories,” he says. “Turnaround time is vital, if it has an influence on that, it’s worthwhile.”
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