Perhaps that is what some mean and if so, they are using it incorrectly. A False Negative has a specific definition: one obtains a negative reading when one does have the condition, whether contagious or not contagious. In other words, someone could have full blown covid (per a PCR test) and still get a negative test result on an antigen test bcos the PCR has fewer false negatives.
Epi 101.
Rapid PCR tests are plentiful in my town; results in ~20 minutes. Came back from visiting relatives over the holidays where I picked up a really bad cold. Thought for sure it had to be covid, so was tested 3x over a 10 day period with Rapid PCR tests. All negative.
I had Covid for the first time a few months ago. Flu was going around my youngestâs class and I felt off one evening, though could not really pinpoint anything specific. I tested negative on a rapid Covid test but decided to do a drive-through PCR test just so I could add on the flu test at the same time. I continued testing each day with rapids and continued to be Covid negative. To my surprise, a few days later my flu test came back negative but my PCR test was positive for Covid. I kept testing with rapids each day to see when I would get a rapid positive but tested negative on rapids every single day. I had no other symptoms other than that very first evening where I felt tired and had chills and would have completely missed that I had Covid had I not done the PCR test. Iâm convinced there are a ton of false negatives happening and that most people arenât as diligent as I was and just assume they are negative and never find out for sure.
Another possible explanation for a false negative result is user error. To make sure youâre testing correctly, read through the instructions first, even if you think you know what youâre doing.
âA lot of us this far into the pandemic have done tests multiple times, and itâs easy to be like, âYeah, yeah, I know what to do,ââ Dr. Hafer said. âPulling out those instructions and really making sure you go through it step by step is the best thing to do because each test is a little bit different.â For example, tests may differ in terms of how long you need to swab each nostril, how far up your nose you should go, how many drops to use on the test strip and how long you need to wait for a result.
Another tip is to blow your nose beforehand. Tests for Covid-19 detect the virus in the cells that line the inside of your nose, not in your mucus, so you donât want your snot getting in the way of the sample. Also, make sure youâre going far enough up inside your nose.
âThe most important thing you can do to improve the accuracy of the tests is get a good sample,â Dr. Campbell said. âIf youâre swabbing up there where it burns just a little bit, that tells you youâre doing it right.â
For the most part, though, people seem to be pretty good at self-testing. One of the few studies that compared test accuracy between health care professionals and people swabbing themselves found no difference in rapid test results. Another study found that children as young as four were able to swab themselves proficiently, with test results matching a health care workerâs swabs 98 percent of the time.
Accuracy doesnât appear to be changing with each new variant. Several studies have found that rapid tests performed just as well on the first Omicron variant as they did on earlier strains of the virus. And although there isnât data yet, the experts say thereâs no reason to think that more recent subvariants like BA.5 and XBB.1.5 are any different*.* Thatâs because most of the mutations occur in the spike protein, which the virus uses to enter and infect a cell. Rapid tests detect a different kind of protein, called a nucleoprotein, that has undergone many fewer changes.
âBecause the tests are designed to detect nucleoprotein, and because nucleoprotein hasnât been mutating, we can be pretty confident that the tests are going to still be able to perform as well as they have in the past,â Dr. Hafer said.
If you think you have Covid-19 but test negative, Dr. Hafer recommended waiting 48 hours and testing again. However, if you are over the age of 50 or have a pre-existing condition, Dr. Drain advised getting a PCR test as soon as possible so you can begin taking the antiviral drug Paxlovid if you are positive. Paxlovid can reduce the risk of severe illness, but the medication needs to be started within the first five days of an infection. âThe earlier one starts Paxlovid, the more beneficial it would be,â Dr. Drain said.
If you feel awful but youâve tested negative on three rapid tests in five days (or if you have a negative PCR test), you could be infected with another virus, like influenza or R.S.V. Regardless of whatâs making you sick, itâs important that you stay home until you feel better so that you donât infect other people.
The end
People also have false positives on PCR tests. We all forget that. I knew someone whose child had a positive PCR and they assumed the whole family had COVID (they were all sick) despite the fact that they all tested repeatedly negative on rapid tests. When I gently suggested that it was more likely the PCR test was a false positive than that they had multiple false negatives across multiple brands of tests across multiple family members on multiple days she was stunned - had never occurred to them. They just assumed the rapid tests werenât working well. But weâve always known a certain number of PCR tests are false positives (not a lot, but it happens). In my case I felt sick on day 1, tested negative, tested positive with a light line the following morning. Line was dark by that evening, and was dark for days (at least day 9 or 10, was then getting lighter and I ran out of tests) even though I felt basically fine by day 3 (took the dog for a hike in the snow on day 3, worked from home all week, felt essentially normal with slight stuffy nose and occasional cough. But that test sure was positive!).
I must admit that thought hadnât even occurred to me, since I did feel off that one evening and just assumed the reason I never had any further symptoms was due to being vaccinated/recently boosted with the bivalent booster. No one else in the house ended up with it (we did multiple PCR tests on everyone just to be sure since we have a high-risk family member) but I had just attributed that to my viral load likely being so low that I wasnât really contagious (and hence why I could never get a positive antigen test). I will say that I was quite surprised to be the one lone family member to have caught it since Iâm the one who works from home and had only left the house one time in the week leading up to my positive.
That is what antigen tests are useful for: checking if you are likely to be contagious (which is different from being infected).
But was that one time a time when you went into a crowded indoor place?
A PCR false positive could be due to an unnoticed infection in the previous few months, where the PCR test gives a positive result on dead virus bits.
Donât forget that a PCR test can detect minute covid virus fragments long after you had covid. The home antigen test is more specific to the time of the test.
The second test was the following day. I felt a little weird. A little lump of goo stuck in my throat and my heart was beating a little fast. This time, the whole thing stayed all pink, but you could kind of see where it was darker where the control line should be. I called that negative.
The third test was the next day. I was definitely sick. I completely lost my voice and had a layer of congestion stuck in my sinuses. This time the whole thing turned pink again, but I couldnât see anything where the control line should be. If I really used my imagination, you might have said there was a line where the positive line should be, but definitely not 2 lines. I went to walmart and bought a binax test. Lit up perfectly positive almost immediately.
I follow every set of instructions to a T. But if people are getting results like this, who knows what they might think.
And to all of those over it in 2 days, I hate you. I still have no Voice and donât seem to be getting any better. Maybe Iâll be permanently mute.
Yes, I have used MaximBio tests (not the only brand that I have used).
I did not see the whole strip turn pink before the C and T (if positive) lines appeared. The C line always turned pink for me, as it should. In general, if you do not get a C line (for any brand of rapid antigen test), the test attempt was invalid (i.e. no result, not positive or negative). Was the test kit expired?
However, one thing I have seen is that, long after the 15-30 minute window to read the test, an extremely faint T line may appear, even though no such line was visible within the 15-30 minute window (the instructions explicitly say not to read the test outside of that window). By the instructions, that counts as a negative result, but could it mean a very low level infection?
The expiration says 2-28-25. I checked at 18 minutes using a stopwatch to make sure itâs past 15. I never check past 30. I read the instructions throughly first and then again step at a time as I do them. Iâm anal that way
I donât think I had a level low level of infection if the binax test popped up perfectly positive in a couple of minutes 30 minutes after taking this one. I think I got garbage tests.
The absence of a C line on a non-expired test suggests a defective test.
For that one perhaps, but all 3 were very weird with the whole strip remaining pink. Iâve never seen a test do that before, but I hadnât used this type before.
âCOVID-19 has both direct and indirect impacts on cardiovascular health. As we learned, the virus is associated with new clotting and inflammation. We also know that many people who had new or existing heart disease and stroke symptoms were reluctant to seek medical care, particularly in the early days of the pandemic. This resulted in people presenting with more advanced stages of cardiovascular conditions and needing more acute or urgent treatment for what may have been manageable chronic conditions. And, sadly, appears to have cost many their lives.â
This probably surprises no one, and lest anyone reading think about blaming vaccines Iâll add the gentle reminder that there were no Covid vaccines for the general public in the US in 2020 until Dec, and in Dec only limited people could get them.
Yep. Iâm pretty sure I can pinpoint the exact five minutes spent in a crowded, tight space where I caught it. I really think that was when I caught it rather than an unnoticed infection in the previous few monthsâŠsince we have a high-risk family member, I typically do PCR tests pretty frequently and because I had traveled the month before, I was really on top of PCR testing during that time. Iâm fairly certain this was my first infection.
interestingly my boss and i were chatting. Mind you both of us attended in December a trade show with 40K people and came out unscathed. He had just gone to the Uhaul place to get boxes. It was crowded and he said he would not be surprised if he caught covid. Sure enufâŠ
i am so confused now about when someone is contageous . It used to be that before the tests were positive/when you had symptoms you were contageous. Now we are saying only when there is enough viral load for an antigen test to test positive? did the vaccines change this?
I know last Wednesday a friend tested positive. I had seen them Monday night. I was sure that was it.
It hasnât really changed:
However, vaccination sometimes results in symptoms before the viral load reaches the level of being detectable by rapid antigen test, since symptoms may be an early immune reaction.
Per the Cal DH, a positive test AND you are symptomatic presumes that you are contagious.
A positive test when you have no symptoms could be a false negative and one should retest with a PCR or other NAAT.
The vaccines did change things somewhat in that a vaccinated person is more likely to mount a quicker response (since their immune system is already primed to recognize the virus) and therefore they are more likely to show symptoms prior to having a viral load high enough to be contagious.
