Is there any reason not to get the covid antibody test?
November 30, 2020 3:54 PM   Subscribe

I probably didn't have a mild/asymptomatic covid infection but is there any harm in checking with the antibody test?

I get chronic sinus infections that manifest in ways similar to how many people have described mild cases of covid. I had an unpleasant case of something in late March. My region had little covid exposure at the time but I had been around people who had been in areas that were starting to have outbreaks, including a conference where at least one person is known to have been infected, but none of the coworkers who were also around those people reported covid-like symptoms. Testing wasn't really available at the time for casual diagnoses, particularly given that I had no fever or cough and since I was in total isolation anyway, I just rode it out.

Antibody testing is available and I'm curious about getting it, both to see if that explained how I felt in March and to measure my current risk (I'm aware that the antibodies appear to fade with time and that having had it does not guarantee immunity).

Are there reasons not to get an antibody test? I know that people are being discouraged from getting active covid tests done casually in my area due to a shortage of kits, appointments, and lab time to process them but haven't seen anything about the antibody testing having similar issues. Any out of pocket cost will easily be covered by FSA money that's past the rollover limit that I didn't spend on physical therapy this summer. Obviously, getting the test done would require a small amount of exposure to someone.

I'm aware of both the false positive and false negative issues with the tests. If I did test positive, I wouldn't start engaging in risky behavior assuming immunity or anything like that. It's more of knowing to put a likely infection on my medical history in case there's any long lasting effects and being able to breath a little easier if I should get exposed (but still take precautions).

The CDC has interim guidelines on the testing but doesn't really have an answer to whether someone that's curious but never had a clear indication of an infection should get one. My state and regional health authorities have no guidance on who should get them, just note that they exist and have some disclaimers about the potential for incorrect results and that one shouldn't assume immunity because of a test.
posted by Candleman to Health & Fitness (5 answers total) 2 users marked this as a favorite
I had the antibody test as part of my blood donation. It was just rolled into the usual post-donation testing they do and I received a letter stating results in 2 weeks.
posted by tipsyBumblebee at 4:03 PM on November 30, 2020 [4 favorites]

I don't think there's any reason not to get a test unless you think it would spur risky behavior. The way I read that CDC document is that there's no reason for an individual to get one. I was really excited about the prospect a few months ago but now I'm not sure it really means anything. I wouldn't engage health care resources to get one. The blood donation is a good idea.
posted by wnissen at 4:32 PM on November 30, 2020 [1 favorite]

I'm an epidemiologist. I tested positive in an antibody test a few months ago, which means if I had it I either had an asymptomatic case or that weird illness I had in February was covid. I gave plasma for a research group where I work and we ran my blood through four additional antibody tests: two positive, one equivocal, one negative. In short, sure, get an antibody test but there's not much utility in them right now as we don't quite know how to parse the information that comes from them. They're in no way as powerful or meaningful as a test for active infection. Add this to the pile of shrug for 2020.
posted by late afternoon dreaming hotel at 7:31 PM on November 30, 2020 [9 favorites]

The only reason I could really come up with to get one is the opposite of riskier behavior! People who have been infected twice (that we know of) tend to make worse symptoms the second time around which would be something to be aware of if you were exposed or have covid-like symptoms in the future
posted by raccoon409 at 7:36 PM on November 30, 2020 [1 favorite]

FDA has just today revised their answer to this very question in the agency's FAQ document on the matter:

Q: If antibody tests are not used for diagnosis or exclusion of COVID-19 infection, what is their purpose? (Updated 12/2/20)

A: Serology (antibody) tests may detect different types of antibodies. The most common are IgM and IgG. High quality serological tests can help us understand whether a person or population of people have developed antibodies indicative of an adaptive immune response to COVID-19.

Because a serology test can yield a negative test result even in infected patients (e.g., if has antibodies have not yet developed in response to the virus) or may generate false positive results (e.g., if antibody to a coronavirus type other than the current pandemic novel strain is present), antibody tests should not be used in the immediate (or acute) diagnosis of a patient where COVID-19 infection is suspected. That is, these tests should not be used to diagnose acute COVID-19 infection. Using this type of test on many patients may help the medical community better understand how the adaptive immune response against the SARS-CoV-2 virus develops in patients over time and how many people may have been infected. While there is a lot of uncertainty with this new virus, it is also possible that, over time, broad use of antibody tests and clinical follow-up will provide the medical community with more information on whether or not, and how long, a person who has recovered from the virus is at lower risk of infection if they are exposed to the virus again.

Positive results from appropriately validated serology tests that are designed to be very specific to the SARS-CoV-2 virus can indicate whether a patient has had recent or prior COVID-19 infection. In addition, although not everyone who is infected will develop an antibody response, appropriately validated serology tests, when used broadly, can be useful in understanding how many people have developed an adaptive immune response to the virus and how far the pandemic has progressed.

Serology tests can play a critical role in the fight against COVID-19 by helping healthcare professionals identify individuals who have antibodies to SARS-CoV-2 virus and have developed an adaptive immune response. In the future, this may potentially be used to help determine, together with other clinical data, whether these individuals may be less susceptible to infection. At this time, it is unknown for how long antibodies persist following infection and if the presence of antibodies confers protective immunity.

posted by late afternoon dreaming hotel at 9:07 AM on December 2, 2020 [1 favorite]

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