Virologists, can I hack a pooled Covid 19 home antigen test?
January 2, 2022 6:55 PM Subscribe
We have several people in the family who want to do things, like go to school or work, responsibly. We have a small stash of at-home tests which may be hard to replace once they are used up. Can we use one test for several people to potentially reduce the number of tests used? Obviously if a pooled test is positive we'd have to use individual tests to narrow down who is infected, which could make this a moot point, but if the pooled test is negative we may be able to save test kits for future use. .
Is there a critical difference between the tests I have and (expensive) tests sold as "pooled" tests that would somehow invalidate my hacked test? I can't see why it would, but I'm not a virologist or testing expert and defer to those with expert knowledge. I accept that advice may be theoretical and not studied and peer-reviewed. Of course, if there is any definitive data on this subject please point it out! Thank you!
The tests I have are the iHealth rapid antigen tests, and this is for non-symptomatic adults
Is there a critical difference between the tests I have and (expensive) tests sold as "pooled" tests that would somehow invalidate my hacked test? I can't see why it would, but I'm not a virologist or testing expert and defer to those with expert knowledge. I accept that advice may be theoretical and not studied and peer-reviewed. Of course, if there is any definitive data on this subject please point it out! Thank you!
The tests I have are the iHealth rapid antigen tests, and this is for non-symptomatic adults
Not an expert but I've spent a lot of time around PhD level microbiologists. I would definitely not share a swab between different family members and my feeling is that the volume of reagent/the chamber that holds it and the swab is designed for a single swab such that trying to put more than one in at a time would be prone to giving false negatives as would putting in one swab after another.
The early PCR tests where they'd group samples together due to limited capacity worked because there was no direct use of the swabs in the testing process - the chemical processing done on every sample yields an output that could be combined with other outputs that could be combined and tested for signs of Covid.
posted by Candleman at 7:19 PM on January 2, 2022 [3 favorites]
The early PCR tests where they'd group samples together due to limited capacity worked because there was no direct use of the swabs in the testing process - the chemical processing done on every sample yields an output that could be combined with other outputs that could be combined and tested for signs of Covid.
posted by Candleman at 7:19 PM on January 2, 2022 [3 favorites]
If a test doesn’t indicate in its instruction that’s it’s ok for use with pooled samples, it hasn’t been adequately tested with pooled samples. So no, not a good idea.
Some things that can go wrong - one person in the pool has a substance in their sample that interferes with the test - now instead of just their positive being missed, the pooled test will miss everyone in the pool. Another way - tests have a certain minimum amount of virus that they can detect (and the rapid antigen tests may skate very close to this limit) and whatever scheme is used to pool samples may dilute the samples enough so that they fall below the test’s minimum threshold for detecting covid.
In my view (as a COVID test developer), you might as well skip testing if you’re not going to test according to the test instructions.
posted by Tandem Affinity at 7:45 PM on January 2, 2022 [28 favorites]
Some things that can go wrong - one person in the pool has a substance in their sample that interferes with the test - now instead of just their positive being missed, the pooled test will miss everyone in the pool. Another way - tests have a certain minimum amount of virus that they can detect (and the rapid antigen tests may skate very close to this limit) and whatever scheme is used to pool samples may dilute the samples enough so that they fall below the test’s minimum threshold for detecting covid.
In my view (as a COVID test developer), you might as well skip testing if you’re not going to test according to the test instructions.
posted by Tandem Affinity at 7:45 PM on January 2, 2022 [28 favorites]
tests have a certain minimum amount of virus that they can detect (and the rapid antigen tests may skate very close to this limit)
I think this would be the big problem. Every rapid ag test I've used has warnings like "failing to [swab your nostril for X seconds/swirl the swab in the reagent X revolutions/etc.] may result in a false negative" at every step. And rapid tests already only correctly report a positive result around 60% of the time for the infected but asymptomatic. If you're messing with the protocol, I think your results are going to quickly become meaningless.
posted by pullayup at 8:52 PM on January 2, 2022 [4 favorites]
I think this would be the big problem. Every rapid ag test I've used has warnings like "failing to [swab your nostril for X seconds/swirl the swab in the reagent X revolutions/etc.] may result in a false negative" at every step. And rapid tests already only correctly report a positive result around 60% of the time for the infected but asymptomatic. If you're messing with the protocol, I think your results are going to quickly become meaningless.
posted by pullayup at 8:52 PM on January 2, 2022 [4 favorites]
We did exactly this before Christmas, in order to make a limited number of tests cover our more extended (and all vaccinated/boosted) family. My sister and her husband, both MDs who've been in the thick of COVID response, suggested it and administered the testing/beer/firepit in our driveway. Family units (i.e. a couple, or a couple and their kid at most) would share a test.
And yes, the assumption is that people sharing a swab are people who are already in close enough contact that if one were positive, the others would have already been exposed.
posted by jeffjon at 5:59 AM on January 3, 2022
And yes, the assumption is that people sharing a swab are people who are already in close enough contact that if one were positive, the others would have already been exposed.
posted by jeffjon at 5:59 AM on January 3, 2022
And yes, the assumption is that people sharing a swab are people who are already in close enough contact that if one were positive, the others would have already been exposed.
I realize that you're saying MDs decided to do this, but it's worth pointing out that the percentage of close contact family members who actually end up becoming positive from other family members is nowhere near 100% even with Omicron, and at least with prior variants was lower than that with asymptomatic cases (and I would hope you're not sharing nose swabs with a symptomatic person). Putting the virus directly into your nose seems like a great way to make those odds of family infection much higher. It's such a bad idea.
posted by ch1x0r at 6:27 AM on January 3, 2022 [16 favorites]
I realize that you're saying MDs decided to do this, but it's worth pointing out that the percentage of close contact family members who actually end up becoming positive from other family members is nowhere near 100% even with Omicron, and at least with prior variants was lower than that with asymptomatic cases (and I would hope you're not sharing nose swabs with a symptomatic person). Putting the virus directly into your nose seems like a great way to make those odds of family infection much higher. It's such a bad idea.
posted by ch1x0r at 6:27 AM on January 3, 2022 [16 favorites]
Have worked in public health, but not an MPH or virologist. Would you trust a negative home pregnancy test that a multiple people had peed on?
Trusting a negative test that has been misused doesn’t just expose you and your family to the risk that it’s a false negative and you’ve just infected each other in the most direct way possible: it exposes everyone you come in contact with.
For the past year, thousands upon thousands of health workers have avoided infection with rigorous masking and hygiene protocols. If you can’t afford regular testing for everyone in the family, what else can you do to amp up or ensure consistent and comprehensive prophylaxis? Are you wearing KN-95s, and switching them out frequently? Are you washing your hands all the time, holding back from picking your noses or teeth or eye-boogers? Have you turned on your local exposure notification apps? Are you minimizing the time you spend inside with other people? In the end, these actions are far more likely that even regular home testing to prevent your own infection or your family infecting others.
posted by rrrrrrrrrt at 2:18 PM on January 3, 2022 [4 favorites]
Trusting a negative test that has been misused doesn’t just expose you and your family to the risk that it’s a false negative and you’ve just infected each other in the most direct way possible: it exposes everyone you come in contact with.
For the past year, thousands upon thousands of health workers have avoided infection with rigorous masking and hygiene protocols. If you can’t afford regular testing for everyone in the family, what else can you do to amp up or ensure consistent and comprehensive prophylaxis? Are you wearing KN-95s, and switching them out frequently? Are you washing your hands all the time, holding back from picking your noses or teeth or eye-boogers? Have you turned on your local exposure notification apps? Are you minimizing the time you spend inside with other people? In the end, these actions are far more likely that even regular home testing to prevent your own infection or your family infecting others.
posted by rrrrrrrrrt at 2:18 PM on January 3, 2022 [4 favorites]
+1 to rrrrrrrrrt's point.
Assume that the answer to "can we use our at-home tests in a way that's not advised by the experts that designed them" is "no". At-home rapid tests are not intended to be a "go ahead and do that thing" free pass, anyway. They're supposed to be used to monitor population health and asymptomatic cases alongside taking other precautions.
The absolute best thing you can do in order to allow your family members to go to school and work responsibly is for them to stick to the guidelines:
- wear masks (ideally FFP2/FFP3 if you want to be really secure, but at least a surgical grade mask; not just a fabric mask) at all times around other people
- make sure as many spaces as possible are adequately ventilated (this is more important than distancing)
- where the above isn't possible, at least reduce the number of people in those spaces and reduce the time spent in the space
- avoid public transport if possible
- isolate as much as possible when not at work/school, so no going out to eat/going to bars/movie trips/frivolous shopping trips etc
- if they get any cold symptoms at all, isolate and PCR test
Doing all of these things isn't a guarantee of avoiding infection but it's much, much more effective and safe than just acting "normally" and using rapid tests.
posted by fight or flight at 2:31 PM on January 3, 2022
Assume that the answer to "can we use our at-home tests in a way that's not advised by the experts that designed them" is "no". At-home rapid tests are not intended to be a "go ahead and do that thing" free pass, anyway. They're supposed to be used to monitor population health and asymptomatic cases alongside taking other precautions.
The absolute best thing you can do in order to allow your family members to go to school and work responsibly is for them to stick to the guidelines:
- wear masks (ideally FFP2/FFP3 if you want to be really secure, but at least a surgical grade mask; not just a fabric mask) at all times around other people
- make sure as many spaces as possible are adequately ventilated (this is more important than distancing)
- where the above isn't possible, at least reduce the number of people in those spaces and reduce the time spent in the space
- avoid public transport if possible
- isolate as much as possible when not at work/school, so no going out to eat/going to bars/movie trips/frivolous shopping trips etc
- if they get any cold symptoms at all, isolate and PCR test
Doing all of these things isn't a guarantee of avoiding infection but it's much, much more effective and safe than just acting "normally" and using rapid tests.
posted by fight or flight at 2:31 PM on January 3, 2022
In addition to the other very good advice saying not to do this, I have a non-covid related reason. Staph loves to hang out in moist, warm place like your nose. If anyone in the proposed group of people to be tested has ever had a staph/impetigo infection in or around their mouth or nose, it would be an extremely bad idea to share a nasal swab.
posted by i feel possessed at 2:52 PM on January 3, 2022 [5 favorites]
posted by i feel possessed at 2:52 PM on January 3, 2022 [5 favorites]
Response by poster: Interesting responses above, with many valid points.
For those who have pointed out that testing does not take the place of other mitigation measures - I know. We are already on them. Omicron appears to have changed the rules.
For those who have emphasized that no studies support using tests in ways they have not been approved for - I know.
For those who have suggested that sharing swabs is a BAD IDEA - I know, and never considered it. Ick and double ick, besides the obvious risk of creating a virus vector. I should have stated this clearly in my original post. The swabs themselves may be the most limiting item in my hacking scheme, though. Tests are studied and validated using specific swabs and substituting, say, Q-tips, could itself invalidate the results. The swabs I've used from test kits appear to be non-absorbent, which Q-tips are not, and the tests come with one swab only. The swab question is an unknown unknown, but with access to additional approved swabs I still think the pooling idea has merit and deserves study.
I only thought about the pooling possibility because home tests are so, so hard to find in my area. I was in a pharmacy this morning that had been turning people away for days for lack of stock, when UPS delivered a box of 300 single tests. The pharmacy has been scouring suppliers for several days trying to locate legitimate stock at a reasonable price. In any case, 300 tests at 20% higher price than last week's tests were sold out in 5 hours, though the pharmacy imposed limits to allow more buyers. All gone.
However we approach it we need to solve the problem of too few tests, but it seems hacking a pooled test isn't the answer. Thanks everyone for your insights.
posted by citygirl at 9:53 PM on January 3, 2022
For those who have pointed out that testing does not take the place of other mitigation measures - I know. We are already on them. Omicron appears to have changed the rules.
For those who have emphasized that no studies support using tests in ways they have not been approved for - I know.
For those who have suggested that sharing swabs is a BAD IDEA - I know, and never considered it. Ick and double ick, besides the obvious risk of creating a virus vector. I should have stated this clearly in my original post. The swabs themselves may be the most limiting item in my hacking scheme, though. Tests are studied and validated using specific swabs and substituting, say, Q-tips, could itself invalidate the results. The swabs I've used from test kits appear to be non-absorbent, which Q-tips are not, and the tests come with one swab only. The swab question is an unknown unknown, but with access to additional approved swabs I still think the pooling idea has merit and deserves study.
I only thought about the pooling possibility because home tests are so, so hard to find in my area. I was in a pharmacy this morning that had been turning people away for days for lack of stock, when UPS delivered a box of 300 single tests. The pharmacy has been scouring suppliers for several days trying to locate legitimate stock at a reasonable price. In any case, 300 tests at 20% higher price than last week's tests were sold out in 5 hours, though the pharmacy imposed limits to allow more buyers. All gone.
However we approach it we need to solve the problem of too few tests, but it seems hacking a pooled test isn't the answer. Thanks everyone for your insights.
posted by citygirl at 9:53 PM on January 3, 2022
“I think the pooling idea has merit and deserves study”.
That study cannot be done by people trying to “hack” the pandemic at home.
posted by rrrrrrrrrt at 10:34 PM on January 3, 2022 [1 favorite]
That study cannot be done by people trying to “hack” the pandemic at home.
posted by rrrrrrrrrt at 10:34 PM on January 3, 2022 [1 favorite]
Pooling does have merit and has been validated for some tests. When a test has been validated with pooled samples, that mode of use will be included in the intended use statement and there will clear instructions for how to test pooled samples. There would also be sufficient supplies to follow the instructions.
posted by Tandem Affinity at 12:07 AM on January 4, 2022 [2 favorites]
posted by Tandem Affinity at 12:07 AM on January 4, 2022 [2 favorites]
The swab question is an unknown unknown, but with access to additional approved swabs I still think the pooling idea has merit and deserves study.
There are already people studying it in far more scientific circumstances than in your own home. As you yourself mentioned, there are already more expensive pooled tests available, so this idea is clearly being considered.
Think of it this way: if at-home tests are so difficult to get hold of, it doesn't make sense to deliberately misuse them or "hack" them in a way that may make the entire test invalid and useless. You're taking a useful test that someone else might need and potentially breaking it for no reason. If you want to conduct this experiment on your own time and with your own money, fine, but please don't do it when at-home testing is both necessary and difficult for many people to access. And please don't do it in a way that might give you false results that might actively spread the virus in your local community.
posted by fight or flight at 5:27 AM on January 4, 2022 [2 favorites]
There are already people studying it in far more scientific circumstances than in your own home. As you yourself mentioned, there are already more expensive pooled tests available, so this idea is clearly being considered.
Think of it this way: if at-home tests are so difficult to get hold of, it doesn't make sense to deliberately misuse them or "hack" them in a way that may make the entire test invalid and useless. You're taking a useful test that someone else might need and potentially breaking it for no reason. If you want to conduct this experiment on your own time and with your own money, fine, but please don't do it when at-home testing is both necessary and difficult for many people to access. And please don't do it in a way that might give you false results that might actively spread the virus in your local community.
posted by fight or flight at 5:27 AM on January 4, 2022 [2 favorites]
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There has been a pretty reliably steady supply of tests you can order online from CVS, Walmart, etc. They aren't super cheap but not such a shortage that I don't think you could ever get more if you are able to afford them.
posted by ch1x0r at 7:01 PM on January 2, 2022 [14 favorites]