Are some people prone to false negative Covid tests?

[ArmChairQueen]

My my current situation has got me wondering if some individuals are less likely to produce a positive test result regardless of whether they have Covid .

There is no scientific basis for thinking this but this is my experience:

18 months ago I had classic Covid symptoms including a loss of taste. Tested negative on two PCRs then teen DC tested positive the following week.

Now my other teenage DC has just tested positive on lateral flow and then PCR. I took a pcr when she had hers ( negative- unsurprisingly). But yesterday I developed a streaming ‘cold’ and yet I’m still testing negative on lateral flow. How can I NOT have Covid? And why are my own results always negative even when I have symptoms and have family members with confirmed cases?

Anyone had similar?

Is a false positive more likely to occur repeatedly in some people or is it random, I wonder?

PS at the time of the first case Covid was extremely rare in my area so I can’t believe it was a coincidence that DC got it after my illness

Interesting. 3/4 of us in our household have tested positive for Covid over the Christmas holiday, one after the other. We haven’t been able to isolate from each other as the flat is too small and the children are too young. 11yo DS had the same symptoms at the same time as me, but produced 2 negative LFTs and a negative PCR while I tested positive. I can’t believe he hasn’t actually had it! Unfortunately without an antibody test we’ll never know 🤷🏻‍♀️

Some times people are facing this type of false test report, this will makes more stress and also taking some decision. This is happened in my area also. So people should be calm and cool, when they are receive their test report.

DH had every symptom, raging temp, horrendous cough and no taste/smell. Lots of colleagues positive, he had 2 negative PCRs and all negative lateral flows.

@crushedgrape and @Mrsfrumble sounds like I’m not alone!

Yes, I definitely saw my first experience as a false report @jeffersonsam. But only after DC tested positive and only after returning to work too soon in a school! I felt so guilty as I fully believed the negative result thinking it was flu ( the taste issue developed on day ten after I’d returned to work).

Yes, this happens because a substantial proportion if the false negative rate is directly attributable to technique if the person (self) admisntering the test.

So yes, there will be people who will always get negative results, simply because they are not carrying out the test well enough.

If I have time later I'll dig out some of the papers about the rates (BMJ I think published something on this)

@UnmentionedElephantDildo that’s interesting. I am if anything over zealous when swabbing. I can see how you could get it wrong by swapping too lightly but i do extra rotations of the swab, all around back of the throat and far up the nostril. Where could I be going wrong? Genuine question.

isnt it the timing?

This is really interesting, i tested negative on LTF the day i done my PCR (dp was positive), we both tested at the same time with LTF, his was blazing positive, mine negative. PCR’s the same day, both PCR’s were positive. We both isolated for 10 days, he was so poorly. I had absolutely no symptoms at all and was fine. So strange

Well that would explain DS then! He won’t let me swab for him and insists on doing it himself 😬 For some reason I assumed that if he wasn’t sticking it far enough up his nose he’s get an invalid / inconclusive result.

Anyone have any tips on how to persuade a tween with ASD who thinks he knows it all that he needs to swab more carefully?

Okay so I have done a bit of research on swabbing techniques. It would seem that the type of test we are asked to do as lay people is not the same as the one medics do. We are asked to rotate around the nostril whereas this ‘correct’ technique looks terrifying as a lay person:
jamanetwork.com/journals/jamaotolaryngology/fullarticle/2770786

[quote ArmChairQueen]Okay so I have done a bit of research on swabbing techniques. It would seem that the type of test we are asked to do as lay people is not the same as the one medics do. We are asked to rotate around the nostril whereas this ‘correct’ technique looks terrifying as a lay person:
jamanetwork.com/journals/jamaotolaryngology/fullarticle/2770786[/quote]
Well, I’m due to do a LFT today, so I’m going to give this terrifying-looking technique a go. Will report back.

It’s certainly different from the technique advised in the test booklets. But it does look far superior for collecting the sample.

Don’t do it @SpindleSpangle! It might be dangerous.
This says it’s only for trained healthcare professionals:
www.google.co.uk/amp/s/blog.puritanmedproducts.com/nasopharyngeal-swab-vs-nasal-swab%3fhs_amp=true

Ok if you say so! But I’ll adapt my ‘technique’ a bit to focus a tad more on that area / direction of my snozzle.

I’ve only ever had negative test results despite feeling repeatedly shit since around May 2020 onwards. (Both home PCRs and LFTs.)

@SpindleSpangle I’m going for a pcr and will adapt my technique a bit too but scraping along the tonsils/ back if throat a bit more. It looks like that’d reach the same area as the scary nasal swab!!

I think there's something in your theory. I 100% had covid, backed up by an antibody test a month later (pre vaccinations). I had 4 negative test results, one of which was administered by a professional.

Ooh very interesting!

I also agree that it may well be to do with technique, but then I know heaps of people who've tested positive with pretty cursory swabs. I'm not sure many people can be as thorough as the professionals!! Who could do that to themselves!

This is one the reasons why home tests are never accepted where I live. Only tests administered by trained professionals count as ‘official’. You can’t use home LFTs for event for example.

They do go all the way to the back, like in the article. It’s not pleasant but it’s properly done.

We also don’t have home PCR kits. When you have symptoms or are a close contact, you must get your test done at the doctors or a testing site, where you’re not allowed to swab yourself. The false negative rate is somewhat lower. The only time I’ve seen home PCRs being talked about is for fit-to-fly’s. And they’re not EU-recognised, so not many people use them really.

On top of that, I too believe there are some people that just don’t test positive. They’ll have positive antibody tests after recovering but all their LFTs and PCRs were negative. I’ve seen it happen a fair few times.

We’ve had all manner of bugs in the last 2 years. Multiple PCRs and LFTs come back negative. Maybe something in this theory.

Very interesting indeed… so whilst we hypothesising, perhaps age could be a factor. The only people in my house who’ve tested positive are teenagers. I’ve no idea if this is relevant but wonder if viral load varies with age??

Yes I believe so. In the same way some people secrete lots of virus and are super spreaders, I think some secrete very little (technique in swabbing is another, separate issue). There have been cases of people in hospital with COVID pneumonia (diagnosed by symptoms and xray) from whom several attempts had to be made to get a positive sample.

LFT done.

Well maybe I'm a freak of nature but I found that technique pretty easy to administer once I'd studied and understood the diagram. Certainly got a lot deeper into the nose without mishap or discomfort.

Still negative though! And I feel absolutely crap ... and have a hospital outpatient appointment tomorrow. (Funnily enough, it's a review of my immune-suppressant medication, hence my jumpiness around covid-19.)

But thank you anyway for that very interesting and useful link / advice (and thread.)

I would imagine so. Just like some medications and stuff can affect pregnancy tests and other test results, I'd take a guess that the same can happen with covid tests.

[quote ArmChairQueen]Okay so I have done a bit of research on swabbing techniques. It would seem that the type of test we are asked to do as lay people is not the same as the one medics do. We are asked to rotate around the nostril whereas this ‘correct’ technique looks terrifying as a lay person:
jamanetwork.com/journals/jamaotolaryngology/fullarticle/2770786[/quote]

That is really useful to know - thanks for the link @ArmChairQueen