My quick answer to the question posed in the title is, no. But, this is an opinion based on my interpretation of the data on the likelihoods of the test being positive or negative should you have covid, and the likelihoods of the test being positive or negative should you not have covid. Given this is a controversial claim, I should expose my reasons for this interpretation.
There are principles that guide the use of diagnostic tests. One is that the test may perform differently depending on the chance that a condition is present in the first place. In other words, if there is a severe form of a condition a test may perform differently than if there is a mild form. The chance of having covid will vary with every person, and whether they are sick, how sick, how long they have been sick, or have they been sick at all, for examples. The test will perform differently across this spectrum of variations in clinical situations. For example, in a small study of 30 people receiving both a rapid antigen test AND a gold standard PCR test, the rapid test was negative in every case of true, PCR positive covid in the first 2 days after becoming infected. This is a big problem.
A second principle is that no clinical test is perfect. A perfect test means that the test would return a positive result in every person with a given condition and a negative result in every person without that condition. This is rare, and certainly not the case for covid. What are the imperfections of tests? There are two main ones. First, a test result may return positive even if you do not have the disease, or, second, return a negative result if you do have the disease. In the former happenstance, this is called a false positive; in the second, it is called a false negative.
False positive and negative test results are the bane of clinical care. The consequences of falsely identifying or missing a disease will vary. In fact, in every clinical circumstance, some balance must be made when weighing, or valuing the consequences of false identification or false missing of a disease. Which imperfection is worse is a crucial question. In a pandemic, where a diseased person has a false negative test, the falsely assured diseased person may spread covid. In fact, in the small study I alluded to above of 30 people with both a PCR test (best test) and a rapid test, 4 of those people spread disease with a negative rapid test despite a positive PCR test.
In a pandemic, finding diseased persons is paramount. As the graph at the beginning of this blog shows, the rapid tests fail at finding all diseased persons. There are numerous studies of the tests, many done by those who developed the tests, and a review in 2020 found the false negative rate to be as much as 100% to a low of about 20% across studies. In a more recent review, in 2021, the average false negative rate was about 30% and false positive rate of about 2% when all studies were taken into account.
More damning, in my view, is that there are numerous manufacturers of the tests with varying false positive and negative rates between these manufacturers, and no clear or useful comparisons between the types of tests. I tried to find which tests would be distributed by our government, but could not. It seems different kits may be sent and we will not know which is best. Worst of all, not a single clinical randomized trial of the value of testing has been done. I might be a bit stringent, but, in my view, this fact alone negates any idea of using this test in the general public. In addition, the test results were not appropriately studied in the real world, with the public as the person performing the test.
I hope I am wrong about the value of testing for covid. But, I see patients with negative test results who ultimately are found to have covid. I know that those people spread covid to contacts. I also see those with no symptoms have a positive rapid test who must change their activities and the activities of those they care for.
The consequences of the false positive and false negative test results for covid are not balanced, and unclear. The wide-spread use of the test, given this uncertainty, is scientific hubris. Studying the effectiveness of a testing strategy would have been a better plan than spending billions on tests of uncertain, and unbalanced benefits.
2 thoughts on “Will rapid covid tests help stop the pandemic?”
Patrick Walsh
Maybe this is just my opinion, but it seems to me like a good middle ground would be to teach people how to effectively use the at home tests rather than just handing them to everyone and waving goodbye with the assumption they know how to use the test. As a non-medical professional, if I’m handed a box that says “this will tell you if you have a virus” my initial reaction would be to take it the second I have symptoms to make sure I don’t have the virus if for no other reason than I don’t know how an antigen test should be appropriately used. Maybe that’s a failure on my part to read the fine print telling me to test after a couple days, but I feel in today’s world it’s not too much to ask for a little general info from news outlets on proper testing techniques.
In my own experience the at home tests are a good quick way to determine if I need to quarantine myself without needing to go through the hassle of making an appointment with a place that has open testing slots. It’s a time saver and a helpful tool to tell me quickly if I need to isolate or if I can just mask up and do my necessary errands. It’s a much less useful tool if I have to wait a couple days after onset of symptoms (during which I would have to isolate anyway) to determine if I have Covid or not. All that’s to say, if the test can’t tell me as soon as I get symptoms that I have Covid, then the test isn’t useful to me and I may as well just isolate/wait out any symptoms of illness (which we should all do for any illness anyway) before being around people again. It’d be more helpful if sick people stayed home anyway. It’s hard to infect anyone if you don’t see anyone.
Well thought out. I can’t think of a logical reason for the test. If no symptoms and low likelihood of covid, then a negative test is not helpful and a positive test leaves uncertainty. If you are sick, it may be several days until the test becomes positive and most of the 5 day stay at home is over. One manufacturer’s instructions stated best results for true positive at day 6, which is later than the proposed stay at home with covid. Also, if you are sick with any other communicable disease, like flu, you should stay home until well. Last, I think testing just extends, and worsens, the social/economic consequences of the persistent fear of this pandemic which is over; covid is endemic. We will have to act with covid much like we act with flu. It is time to move on.
Maybe this is just my opinion, but it seems to me like a good middle ground would be to teach people how to effectively use the at home tests rather than just handing them to everyone and waving goodbye with the assumption they know how to use the test. As a non-medical professional, if I’m handed a box that says “this will tell you if you have a virus” my initial reaction would be to take it the second I have symptoms to make sure I don’t have the virus if for no other reason than I don’t know how an antigen test should be appropriately used. Maybe that’s a failure on my part to read the fine print telling me to test after a couple days, but I feel in today’s world it’s not too much to ask for a little general info from news outlets on proper testing techniques.
In my own experience the at home tests are a good quick way to determine if I need to quarantine myself without needing to go through the hassle of making an appointment with a place that has open testing slots. It’s a time saver and a helpful tool to tell me quickly if I need to isolate or if I can just mask up and do my necessary errands. It’s a much less useful tool if I have to wait a couple days after onset of symptoms (during which I would have to isolate anyway) to determine if I have Covid or not. All that’s to say, if the test can’t tell me as soon as I get symptoms that I have Covid, then the test isn’t useful to me and I may as well just isolate/wait out any symptoms of illness (which we should all do for any illness anyway) before being around people again. It’d be more helpful if sick people stayed home anyway. It’s hard to infect anyone if you don’t see anyone.
Well thought out. I can’t think of a logical reason for the test. If no symptoms and low likelihood of covid, then a negative test is not helpful and a positive test leaves uncertainty. If you are sick, it may be several days until the test becomes positive and most of the 5 day stay at home is over. One manufacturer’s instructions stated best results for true positive at day 6, which is later than the proposed stay at home with covid. Also, if you are sick with any other communicable disease, like flu, you should stay home until well. Last, I think testing just extends, and worsens, the social/economic consequences of the persistent fear of this pandemic which is over; covid is endemic. We will have to act with covid much like we act with flu. It is time to move on.