Hey Jolly - help me with some lab result interpretations
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As you know I've been getting antibody tests regularly for months. Over a year, actually.
Up until the most recent one, I've been getting Labcorp's SARS-CoV-2 Antibody, IgG, Spike (164055). They give only a positive or negative result. All mine have been negative.
My last test was the SARS-CoV-2 Semi-Quantitative Total Antibody (164090). This one, as the name suggests, gives a titer as well as a Positve/Negative.
Well the good news is this one showed me positive, at 3.3 AU/ml, with the cutoff for positive being 0.8 AU/ml.
My first reaction was "great, I'm way into positive territory!"
But then I started thinking about it. My last IgG Spike test was 73 days after my booster. I took the semi-quantitative test 10 days later.
How could one be negative and one be positive? Well, the possible answers (short of outright error) seemed to be:
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My body didn't develop antibodies until 74+ days after the booster. Seems really unlikely. Average is 8-11 days.
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I had a recent exposure with no symptoms. Perhaps a bit more plausible, but still very unlikely.
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The two tests have different thresholds, and thus there is a range of antibody levels that will get differing results from the two tests.
The more I thought about it, the more I figured #3 is what is going on here. I tried to compare the units of the two tests, but they are arbitrary and incomparable. (in fact, AU/ml means "arbitrary units per ml")
So then I tried to see what a 'typical' positive result would look like. I mean a normal person vaccinated in the last few months.
Labcorp specifically say they don't know what level is protective. Fair enough. So I wondered if they would at least publish a range of 'typical' results for recently vaccinated people. No dice.
I do have two hints though. In the sample reports they publish, their sample positive report shows an antibody level of 2490.1 So much for my 3.3!
The other hint - there's a research study that was looking at the linearity of results from that particular test, which describes a result <20 as 'very low'.
So I think all of the above nets out to "I have some antibodies, but its a very low level and I probably can't rely on it for much at all".
My specific questions to you:
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Do you see any particular flaw in my reasoning?
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Do you have a way of finding out what 'typical' values of that semi-quantitative test might be for "normal" vaccinated people? IOW, can you confirm my conclusion that 3.3 is in fact a very low result?
The Labcorp semi-quantitative test is this one.
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No expert here.
Number 3 makes sense.I think u can’t compare lab kits one to another. Each one has its own sets of parameters and thresholds etc…. The usefulness is when u have a population all using the same kit, so for example in my hospital everyone gets their serology done by the same kit and so we peons can compare our antibody levels one to another but it’s not translatable to other tests.
Btw I had serology done after shot 3. Went way up but not quite as high as when I checked after shot 2.
My numbers were January 31.28 March 14.47. April 9.2 May 6.2 June 3.76 the day I got the third shot in August 1.15
Now 8 days post third shot 19.78.Threshold was 0.8 for positive.
Truth is I have no fucking clue what it all means. People around me are getting infected all the time.
We also now have rapid antigen swab tests, results in 15 min, which we do periodically when possibly exposed.
I think we are all fucked one way or another. By the time the delta strain gets its own particular vaccine, another variant will be spreading.
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@bachophile said in Hey Jolly - help me with some lab result interpretations:
I think we are all fucked one way or another. By the time the delta strain gets its own particular vaccine, another variant will be spreading.
Any attenuation possibilities?
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By the way the units given for me is S/CO which in my infinite ignorance I had to look up and means signal to cutoff ratio.
Like I said, I’m no expert. Clueless in fact.
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Attenuation. When it all started I honestly believed that when viruses mutate, they change to maybe more contagious but less virulent.
So much for that pearl of wisdom.
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@bachophile said in Hey Jolly - help me with some lab result interpretations:
I think u can’t compare lab kits one to another. Each one has its own sets of parameters and thresholds etc…. The usefulness is when u have a population all using the same kit, so for example in my hospital everyone gets their serology done by the same kit and so we peons can compare our antibody levels one to another but it’s not translatable to other tests.
Yeah, I'm clear on that point. I'm really trying to figure out what the range is of this particular test. I'm not even sure who's device it uses. The IgG spike test uses the DiaSorin Liaison product. But I can't find the detail behind the semi-quantitative test.
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@bachophile said in Hey Jolly - help me with some lab result interpretations:
I think u can’t compare lab kits one to another. Each one has its own sets of parameters and thresholds etc…. The usefulness is when u have a population all using the same kit, so for example in my hospital everyone gets their serology done by the same kit and so we peons can compare our antibody levels one to another but it’s not translatable to other tests.
This.
Helps to stick to one kit. The good news is that you finally have antibodies and this test is looking for those antibodies specific to the spike proteins. The bad news is that even though your result is in the positive range, the titers on these type tests don't tell you how much immunity or non-immunity you have. They are best used in a monitoring process, watching the units go up or go down.
Using a Siemens test on a Dimension platform, my antibodies run about 9000, after COVID and two shots of Pfizer. OTOH, the highest antibody titer in our small hospital belongs to one of the medtechs who had a pretty good round of COVID and her titer is 144,000, after two shots of Pfizer (but she had a helluva reaction to the shot). Just looking at tests ranging over a pretty good swath of individuals with vaccine status of none, one and both, there seems to be no definitive number to hang your hat on. Again, longitudinal monitoring.
And for the coup de grace, Bach and George could run rings around me. There is no M.D. behind my name. I'm just a dumb labrat.
EDIT...Without calling them up, I'm not sure which test and platform LabCorp uses. But a SWAG is that it is the Roche.
https://diagnostics.roche.com/global/en/products/params/elecsys-anti-sars-cov-2.html
Always remember, Operation Valkyrie was an act of sedition.
Warning: I post things that interest me. Read and comment at your own discretion. -
@jolly said in Hey Jolly - help me with some lab result interpretations:
Bach and George could run rings around me. There is no M.D. behind my name. I'm just a dumb labrat.
You don't give yourself enough credit.
I don't know jack shit about this stuff.
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@jolly said in Hey Jolly - help me with some lab result interpretations:
EDIT...Without calling them up, I'm not sure which test and platform LabCorp uses. But a SWAG is that it is the Roche.
https://diagnostics.roche.com/global/en/products/params/elecsys-anti-sars-cov-2.html
That's my guess too.
My reasoning? The Labcorp spec sheet says this:
Methodology: Electrochemiluminescence Immunoassay (ECLIA)
And when I read through the list of devices with EUAs only the Roche had that acronym in it's attributes:
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The FDA Fact Sheet indicates some ranges of samples. Varies by system and sample even within the Roche devices, but my number isn't as bad as I thought. Low positives are in the 1.x range, and positive samples averaged anywhere from <5 to 20. Not inconsistent with Bach's results.
This is for the Cobas e 401
