2 positive Lateral Flow Tests - likely to be positive PCR test?

[HelenHywater]

I know I'm being impatient, and I'll know soon, but is there any chance that a PCR test will come back negative if the LFT was positive?

My dd(9) has high temp, headache and stomach ache and I tested her this morning when I realised those were symptoms of the delta variant. We're isolating and have no plans to leave the house until the PCR test comes back but what are the chances of a negative PCR test?

I got two positive LFT and a negative PCR.

I'd still do the PCR though and if it's negative and symptoms persist I'd still test again before returning

Almost zero.

LF tests very rarely give false +ves.

Pushed post too soon* before returning to school / work just to be safe

yes she did the PCR test this morning (and I did too just to be sure, although I had a negative LFT and am doubly vaccinated...) and none of my children are going back to school or out until the results come back.

I had two positive LFT's followed by a positive pcr. Was the same for my partner

If the PCR test is negative are you just meant to go with that?

DS recently had two positive LFTs (from two different packs) but negative PCR. Test and protect told us that the negative PCR meant we could 'stand down' and stop isolating.

@strangeshapedpotato

Almost zero.

LF tests very rarely give false +ves.

Last week one of my closest friends had two positive LFT which was a negative PCR

I thought the accuracy of LFT was only about 82%? So actually it’s a high chance it’s a false positive

@PurpleyBlue

If the PCR test is negative are you just meant to go with that?

You see I don't know. She was sobbing when she did the PCR test as she really hated putting it up her nose/down her throat. I can't really see that she did it properly. Then again, she did the same with the LFTs and they came up positive.

Lateral flow test is one in a thousand chance of a false positive.

2 in a row (with separate swab/sample) - the odds are pretty damn low!

Accuracy of a LFT in terms of positivity is 68%

So get 100 Covid positive people, make them all do a LFT, and 68 will come back positive.

@TattyDevine

Lateral flow test is one in a thousand chance of a false positive.

2 in a row (with separate swab/sample) - the odds are pretty damn low!

I don't know enough about what can lead to a false positive but they're unlikely to be independent. I was also under the impression LTFs had very very low chances of false positives (and consequent high changes or false negatives). Interesting to hear from people who have experienced that

very high specificity

The question is of 100 negative people, how many tested positive, not the other way round.

I don't know the answer but was led to believe it's very low, it doesn't find Covid that isn't there. Misses it, yes, but not the other way round.

Hope you're all ok. Putting your vaccine to the test!

The negative predictive value. If I hadn't had a glass of wine I'd attempt to calculate that

The World Health Organization says the “rate of false positives compared to true positive results will be high.

PCRs can have false positives too, actually.
Nothing OP can do but wait.

en.wikipedia.org/wiki/Sensitivity_and_specificity

Give that a read, come back if you have any questions...

Yes LFT's meant to have very low chances of false positives.

Anyway, it's academic for us as her PCR test has come back positive! So we're all isolating for 10 days. Yay!

I also have 3 teens in the house so it'll be interesting to see if they get it. (and me with my vaccine). Luckily, apart from school last week, I don't think she saw anyone over the weekend. The teenagers on the other hand....

@HelenHywater oh no, hope your DD is okay and no one else catches it OP

@HelenHywater

Yes LFT's meant to have very low chances of false positives.

Anyway, it's academic for us as her PCR test has come back positive! So we're all isolating for 10 days. Yay!

I also have 3 teens in the house so it'll be interesting to see if they get it. (and me with my vaccine). Luckily, apart from school last week, I don't think she saw anyone over the weekend. The teenagers on the other hand....

How did it go please? I am in a similar situation - 2x positive LFT and PCR being done in the morning

Anecdotally, DD had 2x positive LFT. Did PCR, symptoms have since developed and (very slow to return) PCR is also positive.

She has had 1 jab, but less than 14 days ago. Double vaccinated DH and i are waiting with trepidation.

DS9 had 2 positive LFT on Thurs, PCR just came back negative today. He had cold symptoms which is why I did the LFT. I have caught the cold off him and tested negative on LFT.

Not if it was 2 positives on the lateral flow, if the pcr comes back negative I would retest again

LFTs show positive if they get orange juice on them, and I'm fairly sure orange juice does not have covid

@Themeparklover

Not if it was 2 positives on the lateral flow, if the pcr comes back negative I would retest again

I did two more LFT tonight out of curiosity and both negative - this whole situation is confusing. Hopefully a negative PCR for us all tomorrow. DH has had 6 negative LFT in the past 3 days, we are a bit test frantic at the moment due to the worry