COVID Antigen Test: Positive, inconclusive, or not positive?

Which does this antigen test indicate?

  • Pos

  • Inconclusive

  • Neg


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DainBramaged

Lifer
Jun 19, 2003
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Question:

Understanding that a test never definitively indicates positivity, negativity, or otherwise, from the enclosed photos, would you judge this rapid antigen test indicates (and ONLY indicates):

1. COVID Positivity;

2. COVID Inconclusivity (pretty sweet word, right?); or,

3. COVID Negativity.atot01.jpgatot02.jpg
 
Last edited:
Dec 10, 2005
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I would say that based on that test, which appears valid given the control line, that per that testing method, COVID was not detected (not even a faint line).

However, given the sensitivity of these tests (ability of the test to detect positive cases and not give a negative result), you could still be positive. These antigen tests detect about 7/10 cases whereas PCR-based tests will effectively detect 10/10.
 
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DainBramaged

Lifer
Jun 19, 2003
23,410
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81
I would say that based on that test, which appears valid given the control line, that per that testing method, COVID was not detected (not even a faint line).

However, given the sensitivity of these tests (ability of the test to detect positive cases and not give a negative result), you could still be positive. These antigen tests detect about 7/10 cases whereas PCR-based tests will effectively detect 10/10.
I recognize the fallibility of these tests. All I'm asking for is what you believe the test itself indicates, not whether the tested individual is actually positive, not positive, or otherwise.

Thanks for your input. 👍
 
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deadlyapp

Diamond Member
Apr 25, 2004
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I recognize the fallibility of these tests. All I'm asking for is what you believe the test itself indicates, not whether the tested individual is actually positive, not positive, or otherwise.

Thanks for your input. 👍
I would 100% consider that test to be negative.

The positive tests I've seen (even those at the tail end of their detectable window) have a very clear sample line.
 

Muse

Lifer
Jul 11, 2001
33,149
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A bit OT, but here goes (and Watching, because my 4 antigen tests are presumably in the mail):

Are they going to have a means to test if you are exposed to Omicron specifically? It would seem to be possible.
 

deadlyapp

Diamond Member
Apr 25, 2004
6,269
524
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A bit OT, but here goes (and Watching, because my 4 antigen tests are presumably in the mail):

Are they going to have a means to test if you are exposed to Omicron specifically? It would seem to be possible.
No, it requires genome sequencing to determine the strain, which they can and often are doing for some sub-selection of PCR tests.
 

Muse

Lifer
Jul 11, 2001
33,149
5,063
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No, it requires genome sequencing to determine the strain, which they can and often are doing for some sub-selection of PCR tests.
I was wondering if there could be a shortcut. Some assay looking for an omicron specific marker since it has some 50 mutations. I have zero academic training in biology but am not totally ignorant. Ignorant, but not totally! ;)
 

dullard

Elite Member
May 21, 2001
23,809
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A bit OT, but here goes (and Watching, because my 4 antigen tests are presumably in the mail):

Are they going to have a means to test if you are exposed to Omicron specifically? It would seem to be possible.
It is highly unlikely to be doable with antigen tests. Antibodies just are not specific enough. Think of an antibody like a Lego piece. Imagine you have one Lego piece and try to stick it to anything you can find. The Lego piece for the most part is specific enough to only stick to other Lego pieces. It doesn't stick to your couch, or fridge, or pet. But, that Lego piece does stick to many different other Lego pieces. So, it is specific enough to know that if it stuck you have found another Lego, but it can't tell which specific Lego you found.

With PCR you certainly can determine which strain you have. But, as the number of mutations Covid has keeps increasing, PCR just gets really complex to look for all of them.

Sequencing is best once you have a large number of mutations to look for. But, despite the cost of sequencing plummeting in recent years, it is still quite expensive so it is only done occasionally to see what strains are common in the area.

But honestly, the easiest thing we have right now is just your symptoms and timing of what variant is common in your area. Omicron has symptoms like a cold, the other variants (so far) have symptoms like a flu. Those should be pretty easy to tell apart without any tests needed.
  • If you test positive and have some of these: a dry cough, shortness of breath, fever/achiness, or loss of taste/smell then you almost certainly have Delta.
  • If you test positive and have some of these: sneezing, congestion, night sweats, sore throat (especially if it was one of the first symptoms) then you almost certainly have Omicron.
  • Note: you have to be honest with your symptoms here. Many people who claim to be asymptomatic actually had symptoms that they try to explain away (such as "I have a cough due to smoking, thus these extra coughs are not Covid").
 
Last edited:

allisolm

Elite Member
Administrator
Jan 2, 2001
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May I ask why there is even a question on this test? There isn't even the faintest hint of a double line. There is a little blurriness of the positive control (the single line), but it is clearly visible and clearly pink.
This.
 

BarkingGhostar

Diamond Member
Nov 20, 2009
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Curious, how does this type of test whether you previously had COVID, vs. maybe actively having it at the time of the test? More curious if I've even been infected and asymptomatic vs. never been infected.
 
Dec 10, 2005
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Curious, how does this type of test whether you previously had COVID, vs. maybe actively having it at the time of the test? More curious if I've even been infected and asymptomatic vs. never been infected.
This test does not look for your antibodies against COVID. It is a test that is looking for COVID proteins - things only found during an active infection.
 
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DainBramaged

Lifer
Jun 19, 2003
23,410
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May I ask why there is even a question on this test? There isn't even the faintest hint of a double line. There is a little blurriness of the positive control (the single line), but it is clearly visible and clearly pink.

View attachment 56565
The mother of tested individual insisted there was a clear pink line and a very, very faint 2nd pink line. I was incredulous. And then thought maybe I just don't see something because I don't want to see it.

I no longer question my sanity.
 
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dullard

Elite Member
May 21, 2001
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The mother of tested individual insisted there was a clear pink line and a very, very faint 2nd pink line. I was incredulous. And then thought maybe I just don't see something because I don't want to see it.

I no longer question my sanity.
Thanks. I was really curious there. It looks like she doesn't realize that the control line is there for multiple purposes. One purpose is to show how bright the sample line will be when positive. There are some minor lot-to-lot variations in manufacturing so sometimes the two lines are darker or lighter. There is always a second line there. It has applied during manufacturing to react when the sample is positive. The key is does it become a bold pink/purple or not.
 
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