Serology test FAQS and other random musings

So, last week I tested positive for COVID-19 antibodies.  Woot!  Wait ... ?  What does it really mean?  Have I gained a new superpower (alongside my pre-existing superpowers of perfect cadence and mad parallel parking skillz)?

So, coz I'm married to an academic, sister to Dr. Paul Armstrong (SSc) and a believer in science, I did some research.  Here's what I've learned, caveated with the usual blah blah YMMV blah blah don't shoot the messenger blah blah make up your own mind blah blah blah.

How on earth did you get a test?  Aren't they as scarce as hens' teeth?

I got the test at AllCare.  I had to have a tele-dr appt first, but then could walk in to get the test.  I got an appt and the blood draw (vs pin prick) test on the same day.  Extremely easy.  They didn't charge us a co-pay.  My insurance pays 100% for the virus test, and I assume pays for antibody tests (based on my research and comfort with this particular test, I'd pay out of pocket too).  The results came through in 1-3 days.  My positive result came with a caution (see below).

But I've heard that there are lots of faulty tests out there.
How are tests measured?

Essentially, all the serology tests are evaluated on two metrics:

• Sensitivity - how sensitive to detecting the antibodies is it?  The higher % the better.
• Specificity - how accurate is it?  i.e., positive positives vs false positives.  The higher % the better.  This is the key measure.

There are other factors also, but I'm trying to keep this to my level of scientific knowledge, which is roughly that of 5th form School Cert (15-16 yr old).  I dropped all forms of sciences as soon as the system allowed it.

But ... what about this particular test.  Is it approved by the FDA?

FDA has not "approved" any tests.  They've granted "emergency use authorization" for lots of tests.  Academics (bless 'em) are now evaluating those tests against each other using the criteria above.  There is no 'gold standard' against which to evaluate tests.  Eventually, the FDA will approve tests, I assume.

• FDA's list - they have data about all the different tests for which they've authorized for emergency use, including sensitivity and specificity. 
• AllCare's list, talking about what tests they're using and cautioning about what it all means.  They're very conservative - I liked that.

The test that was used for me is the 'Abbott SARS-CoV-2 IgG assay.'  So I plugged that into google and found this academic study from the University of Washington, released a few days ago.  

<science literacy lecture> This test has been through peer review, which means it's several steps above what are know as 'pre-print' studies which haven't yet been peer-reviews.  You'll have seen a tonne of studies from 'pre-print servers' flying around.  Consume those with several grains of salt, and don't listen to or read anything that doesn't mention this fact.   You're looking for studies that have been peer reviewed and accepted for publication. </science literacy lecture>.

Alright already ... get to the results.

The results from the academic study looks great - something like 99.9% specificity.  This means that ONE false positive would be expected in 1,000 tests.  This is about as good as it gets at the moment.  AND, as a bonus, the accuracy increases over time (though not sure how far out that goes).  My test was on Day 51 after first symptoms, so, in the immortal words of Mona Lisa Vito, "dead on balls accurate."

But Mary - we all know how special you are.  Couldn't YOU be the one-in-a-thousand?

Aw, shucks.  You're too kind.  But to answer your question, yeah, sure I could.  But ... combining the test results with the waddles like a duck, quacks like a duck sickness that I had back in March, I'm pretty sure that in this case, I'm one of the 999.

Cautions that came with my results

Caution from Doc:

Good Evening: your covid19 antibody tests came back positive (detected). Your body is producing antibodies in response to past or current infection. please note, we cannot claim you are immune to covid19 based on this test result because 1) there is a small chance this is false positive due to other non-sars coronavirus 2) we do not have evidence that antibody protects you from getting it again

Caution from Lab:

Results suggest recent or prior infection with SARS-CoV-2. Correlation with epidemiologic risk factors and other clinical and laboratoryfindings is recommended. Serologic results should not be used as thesole basis to diagnose or exclude recent SARS-CoV-2 infection. Falsepositive results infrequently occur due to prior infection with otherhuman Coronaviruses. 

This assay was performed using the Abbott SARS-CoV-2 IgG assay.This test has not been reviewed by the Food and Drug Administration.

So ... now what? 

I keep on hearing the same questions, so here they are.

How do you feel about the results? Conflicted.  Not sure why, but there you have it.  Not conflicted as in believing the results, but more - just don't know exactly how I feel.

Are the results meaningful? Yup.  They mean confirmation that I did have COVID-19 in March, 51 days before.  That's all, really.  At this point, the result is a data point at a point in time.  As new studies are done, as more is known about the disease, the result has the potential to mean more over time.  One day I'll know about the actual chances and circumstances of re-infection.

Are the results actionable? Dunno.  Still figuring that out.  

I could see a time when the result may make it easier to cross the border back into NZ.  But that's a year away.  

For now and in the foreseeable future, I'm still going to wear a mask when I'm outside (including when I'm running) coz, you know, that frankly isn't about science for me, it's about being polite and signaling to other people that I care that they don't get coronavirus from me.  I'm too much of a socialist at heart not to try my best to consider the greater good.  I'm still going to practice physical distancing.  I'm still going to do everything I can to not be a vector for the disease to others.

I will carry my results around with me, but I'm not getting a tattoo on my forehead.  I won't go back into the office until I'm forced to (and you can believe that I'll raise holy hell if being public about my results is used agains me) coz of all the above.  I assume that I can still help spread the disease to my 'circle of concern,' if not through coughing or sneezing, but transporting objects etc.

And ... bottom line, if I do choose to take actions based on these results that involve you, I will ask for your consent.  Along with believing in science, I also believe in consent and autonomy.  

Oh, and the last bottom line, as I've learned over the past few weeks.  We're all doing our best.  My best doesn't look like your best or the best of my neighbors.  Please don't scold me for my decisions.  Please don't judge me.  Or if you do, do so silently.  And I'll (mostly) do the same.  

Hope this was helpful!