False positive- drops went in both LFT ‘windows’

[SandalsAndSox]

I am feeling real rough (like a pre cold hangover feeling) so took a lateral flow test.

I accidentally spilled a drop into the wrong window as well as the correct window so did a retest. The ‘failed ‘ test was positive (left) and the retest was negative (middle) and then the ‘control’ that I did by adding the liquid only to the wrong window (without swabbing) showed no result at all (right pic).

I did another test properly took and that was negative too. I have an important meeting tomorrow that must be attended in person.

Would you treat this as a positive result or not? Did I accidentally create a false positive??

It’s not a positive test, it’s an uninterpretable test as was not performed correctly. The 2 you have performed correctly are negative, so I would go to the meeting unless you feel too unwell to do so. Hope you feel better soon.

@Timeforanewoneofthese yes, you’re probably right. I need to reframe how I’m thinking about it!

I would do another test tomorrow. If you keep swabbing your nose for test after test you can easily create a false negative that way.
Could you wear a mask at the meeting?

I’ve no background to back up my opinion but as far as I’m concerned that strip will only react if it’s triggered by the presence of the virus or a couple of other substances that some enterprising teens have discovered.

If you put the actual test solution and nothing else on it then I would say it’s picked up the presence of covid.

Strictly speaking it’s an incorrect test but at the very least I think you need to be extra cautious if you’re going to treat it as a negative.

The virus has to be present for the test line to show up.

Underneath the windows there's a single paper strip. The liquid applied near the bottom absorbs up the strip and the control line is there to confirm that the liquid has absorbed far enough.

Dropping the liquid in the wrong place could cause the ink to smudge or the lines not to show up at all, but I can't see how it could create a false positive line.

There's some evidence that acid and certain chemicals can trigger a false positive, but that would apply where ever the liquid was applied.

Especially as you're feeling unwell, I would wait a few hours or more and test again. As someone else said the repeated swabbing could have removed most of the virus from your throat/nose.

Ooh interesting responses. I hadn’t thought about there being less virus to test if I repeatedly swabbed.

@BlackInk I thought that the thin strip of paper between the windows had been chemically treated in such a way that it reacts with the virus, so the stray drop would not have been tested correctly. Again, as PP said I also have no knowledge of the science involved!

The part of the strip where the test line is is impregnated with something that reacts to the virus (and turns pink). Wherever the liquid is dropped the strip will absorb the liquid and if it reaches the area of the test line it will react if the virus is present.

I can see a line on the middle one.

Oh I see. I thought that part was between the two windows and that the stray drop had therefore not gone through the part that reacts with the virus.

@Tippexy must be something about how the pic uploaded as there was no line in RL

@Tippexy

I can see a line on the middle one.

Yes I can too

If you take a test to bits youl see it’s just a thin strip like those cheap pregnancy tests you can get

the liquid travels along the strip and if the virus is present when the liquid touches the part we’re the T is ( who’s has something on it that causes the reaction not very technical I know sorry 😂 ) it will show the line so I don’t think it matters where about you actually drop the liquid it will travel along the strip

So long story short I’d probably assume positive and maybe leave it untill later tonight / early tommorow and try again

Which not who’s *

The reason you drop the fluid into the S window is so that you can be sure an adequate amount is added: the liquid travels along the test strip and if enough is added to activate the control strip you know enough was present at the test line.
The test line consists of covid antibodies which are bonded to gold molecules. In the presence of covid, the antibodies release the gold to grab onto the covid instead and the gold shows up as a red line. On the control line the gold, which isn’t attached to an antibody, is released by buffer solution alone.
So the presence of a C line means the buffer solution travelled along the test far enough. The presence of a T line means covid was present in a quantity high enough to trigger the release of enough gold to form a visible line.
So test one is positive, whereas test two didn’t have enough covid in the sample to show a line (likely because it hadn’t reproduced adequately since being removed on swab one. Eating or drinking in the hour before a test can have a similar effect)
Test 3 either didn’t have enough buffer solution or had too much at the point of the line so it diffused away. Or it was faulty.

@Howmanysleepsnow very interesting post. Thank you. Do you have a scientific background?
I found this image online and wondered if the sample would have bypassed the ‘conjugate pad’ in my case?

I hate to tell you but I got a positive and negative test within 10minutes of each other last week! The positive was faint, hence why i did the second test while it was still developing. My PCR an hour later was positive. I also had a sore head!

@emmathedilemma I’m guessing you didn’t muck up your test though!
Interesting concept of having less virus due to repeat tests… that could apply in both our cases, perhaps

Do another one later as the decider?!

no i didn't, but it sounds like that might not be the issue!

I had a fainter positive in the afternoon than the morning on the day of my first positive (repeated it as DH pointed out the blood I'd got in the sample may have invalidated it and I was confused by my PCR from the day before coming back negative). It was still there but so faint I'd probably have missed it if I hadn't been expecting it.
If the first test came up immediately I'd say it's probably correct, sorry. Only thing getting the solution in the wrong place might do is mess up the timings i.e. a line that would've shown up after the time might before.

Do one this evening. Take that result as the answer.
I'm surprised the drop in the wrong place created a false positive.
I'm astounded just drops created an invalid test (I've done this, and got a control line, suspect you have a dodgy test strip).

So in the name of science......I currently have Covid. I did a LFT this morning and it was VERY positive.
I've just done one and only dropped the test solution into the results window. Absolutely nothing happens, it looks like your test on the right of the photo. So I reckon your first one was positive.

@emmathedilemma that is soooo interesting. Thank you. I definitely got most of the sample in the correct place btw but some escaped!

it obviously needs sample in the correct window for the "dye" to run up the results strip because it started coming out the wrong way into the sample window. I tried adding some drops to the sample window as well but nothing happened so i either didn't have enough sample liquid left or the dye had already "died" by going the wrong way.

Interesting… will try again later and update