How accurate are rapid home tests? (covid)

[Loowit]

My ILs who travel full time have been sick with "bad colds" for about a week now.  They took the rapid home tests which were negative, so now that MIL is feel a tad bit better she decided to go shopping.  Last night when DH talked to them they were both coughing a lot and sounded not good.  DH is going to call them again tonight to check on them.  I realize it could be just a bad cold, but I was wondering if we should gently suggest they get a test from the doctor's office, just to be safe.  I hate the idea of them out spreading diseases.  And yes, I know it is none of my business and I also know there are other things going around other than covid.

Also, DD was exposed to covid this weekend at her first in person speech and debate tournament she has had since the pandemic started.  One of the members on her team tested positive the day they got back.  They mostly stayed masked but did have some meals together and were on a plane together (masked).  DD is getting tested today with a rapid test and then again in a week.  Since she is vaxed the school said she can be out and about but has to wear a mask (which she would do anyway).  She is so far symptom free.  I am guessing if both tests are negative and she has no symptoms she should be fine.

[Clemsondana]

We actually had a home test be positive and then got a negative result at the pharmacy.  They retested when we were surprised and got a very weak positive, which matches what we got at home (you can definitely tell a strong positive from a weak).  The pharmacy near us said that their antigen test is the same test that we do at home.  We only got tested there because when the first of us thought we might be positive there were not at home tests to be found, and for various reasons it was helpful to have a documented positive test as each of us got sick.  Depending on what state you are in, the current recommendation may be to stay home until you've been fever-free for 24 hours so if they are feeling fine there probably isn't any reason to get a test.  They could always retest at home, too.  And, there are some bad colds floating around right now that aren't covid - we know some people who have been tested multiple times.  

[Laura Corin]

Rapid tests work well if they are taken at the height of transmissability but not so well otherwise.  Tests are free here, so I test daily if I have any symptoms or think I've been exposed. 

[prairiewindmomma]

There's a REALLY bad cold going around in our area.  4/6 of us have had it. All of us have had repeated negative covid tests, so not covid. Both daughters just had a few days of sinus issues. One got conjunctivitis. Neither really had coughing/chest congestion.  This is day 8 for me, and while I don't think I'm headed into pneumonia, I'm still winded just walking across a room. I'm holding steady with the pulse oximeter. I'm taking a lot of meds BUT I'm not on the nebulizer every 4 hours yet. I slept 20 hours a day days 3-6.  I had a low fever days 2-4.  It started as a runny nose, then moved into sinus congestion, and then moved deeper.  I did develop conjunctivitis as well. 

Dd went back to school because she was fever free, had two negative covid tests, and is fully masked.  It feels a bit crazy, but we got a green light from the school nurse.

[itsheresomewhere]

16 minutes ago, prairiewindmomma said:

There's a REALLY bad cold going around in our area.  4/6 of us have had it. All of us have had repeated negative covid tests, so not covid. Both daughters just had a few days of sinus issues. One got conjunctivitis. Neither really had coughing/chest congestion.  This is day 8 for me, and while I don't think I'm headed into pneumonia, I'm still winded just walking across a room. I'm holding steady with the pulse oximeter. I'm taking a lot of meds BUT I'm not on the nebulizer every 4 hours yet. I slept 20 hours a day days 3-6.  I had a low fever days 2-4.  It started as a runny nose, then moved into sinus congestion, and then moved deeper.  I did develop conjunctivitis as well. 

Dd went back to school because she was fever free, had two negative covid tests, and is fully masked.  It feels a bit crazy, but we got a green light from the school nurse.

We had that in January.  It was a really nasty cold. Multiple negative covid tests.  
 

In our experience, the at home tests have been very reliable.  Including when it hit DH’s office and the only symptom the person had was a runny nose.  

Edited March 1, 2022 by itsheresomewhere

[Arcadia]

 

[Loowit]

Thanks everyone.  I am just concerned about them.  My MIL is a social butterfly and loves being out and about around people.  It has been hard for her to be locked down, and now that she has her vaccination she has decided to go back to life as normal.  Most of me thinks it is good she is enjoying herself and their retirement years, but I also worry about their health and being so far from family.

[KSera]

I wouldn’t personally trust a rapid test in the case of either symptoms or a known positive exposure. A PCR is recommended for both of those cases. If your in-laws only tested once at home and that was that, then I wouldn’t take that as a valid measure. It’s very common, especially with omicron, for people to be symptomatic for several days before the home test turns positive. In the very least, they should have followed up with another rapid test 36 hours or so later, as the instructions say. But the general instructions are that if you have symptoms and get a negative home test, you should go get a PCR. If you have symptoms and get a positive, you can just count on it as a positive and not go get a PCR. 
 

whatever it is, I hope they are feeling all better soon and don’t pass it on to anyone else.

[wathe]

@LoowitThe Ontario Covid-19 Science Advisory Table has put out a new brief on RATs and Omicron.  Includes much data on accuracy, and best way to test (oral/nasal vs nasal alone).  It's really good; loads of data, and good graphs, and references. Solid science, written in a way that accessible and meaningful for both experts and non-experts.  

[wathe]

From the brief:

Interpretation

Combined oral-nasal sampling that involves swabbing both cheeks, the back of the tongue or throat, then both nostrils, should be implemented for rapid antigen tests. In light of the high pre-test probability of disease in Ontario and the limited sensitivity of rapid antigen tests for the Omicron variant, a single negative rapid antigen test result should not be used to rule out a case of COVID-19 at this time. Expressed differently, a negative test result is not conclusive and is not a green light for abandoning precautions. However, at the time of writing, a single positive rapid test result can be used to confirm COVID-19. We therefore advise the following for testing symptomatic individuals:

Confirming COVID-19 in the Case of Symptoms

If someone is symptomatic, they are presumed to have COVID-19 and must isolate as soon as possible regardless of rapid antigen test results. If a rapid antigen test is done and is positive, it should be treated as diagnostic for COVID-19. Additional confirmation by PCR is not necessary in most situations. Following a return to work, individuals should wear properly fitted, high-quality masks and practice physical distancing whenever possible.

With the current testing strategy, once the reported rate falls below 50 reported cases per 1 million inhabitants per day (35 per 100,000 per week), 2 out of 3 positive rapid antigen tests could be a false positive. At this point, confirmation of all positive rapid antigen test results by a PCR test should be considered for the general public, and general recommendations on the use of rapid antigen tests should be re-evaluated.

COVID-19 treatment decisions should not be based solely on a positive rapid antigen test. Treatment may be initiated based on a combination of clinical presentation and a positive rapid antigen test, but confirmation by a rapid molecular test or PCR test should be sought in addition.

Ruling Out COVID-19 in the Case of Symptoms

If rapid antigen tests are available to a person with symptoms of COVID-19, they may be used to assess the likelihood that symptoms are due to infection with SARS-CoV-2. A single negative test in an individual with compatible symptoms does not mean that they do not have COVID-19 infection. There are multiple ways in which serial testing can be applied to assess the likelihood of COVID-19, depending on the case rate, risk tolerance, and setting. Options include two consecutive negative tests, separated by 24-48 hours, as is the current provincial guidance,22 or two consecutive negative tests, spaced 3-5 days apart, as suggested by Figure 3. Regardless of the serial testing strategy, current provincial guidance22 states that individuals should self-isolate until they have no fever, and symptoms are improving for at least 24 hours (or 48 hours if gastrointestinal symptoms).

[SKL]

The rapid tests aren't very accurate for Omicron, whether done at home or by a doctor, although I've read that swabbing both the throat and the nose improves accuracy.

I would think that if your folks have been symptomatic for a week, they probably aren't contagious any more even if it is Covid.