Thread by @ChandraPasma

Journalists frequently ask me if my family is pursuing antibody testing to prove we had COVID. Draw up a chair and let me tell you why that question is so problematic.
#Longhaulers #LongCOVID #ApresJ150 #CovidAntibodies

2. A negative antibody test doesn’t necessarily mean you don’t have antibodies and it certainly doesn't mean you didn't have COVID. First of all, the accuracy of C19 antibody tests has been questioned by the CDC and others. Some C19 antibody tests have a high false negative rate.

3. For instance, some of the tests authorized by the FDA have a sensitivity rate under 90% - which means if 100 ppl are tested, 10 or more will be told they don’t have antibodies when they actually do. And that’s the rate reported by the manufacturer, not the rate in actual use.

4. What’s not widely understood though is that the sensitivity was not determined through clinical trials but by using specimens from known #COVID19 patients. In order to get blood samples from known COVID patients back in March and April,

5. most of the samples would have likely come from hospitalized patients. But what if patients who are not sick enough to be hospitalized don’t develop the same level of antibodies? We don’t know what the sensitivity rate is for patients with “mild” cases. ft.com/content/839bed…

6. Furthermore, a study from a consortium of California researchers found that much like PCR testing, the chance of getting a false negative seems to depend in part on the timing of the test: nature.com/articles/s4158….

7. (The same study found that false positives are an even bigger problem for antibody testing, including blood samples from 2018 testing positive for C19 antibodies.)

8. Several studies have shown that C19 antibodies appear to drop off quite quickly, as in 2-3 months after illness. I’ve been sick for 6 months. If I tested negative now, that doesn’t mean that 3 months ago, I wouldn’t have tested positive. cidrap.umn.edu/news-perspecti…

9. The likelihood of receiving a false negative also seems to depend on what type of test is used and whether it uses a finger prick or a blood draw, whether it’s a quick test or a lab test: bmj.com/content/369/bm….

10. In addition to the chance of a false negative, we know that not everyone who gets #COVID19 develops antibodies. In one Chinese study, 6% of people with confirmed COVID infections did not produce detectable levels of antibodies: businessinsider.com/study-recovere….

11. A Swedish study found that among family members who had been exposed to COVID due to the illness of at least one person in the family, family members who tested negative for antibodies still had SARS-CoV-2-specific T cells. cell.com/cell/pdf/S0092…

12. There is some anecdotal evidence to suggest that #Longhaulers are more likely to test negative for antibodies, although because it’s anecdotal, we don’t know why. Timing of tests, for instance? Detection levels? Or is this actually why we experience such prolonged symptoms?

13. And finally, there is also some question as to whether some of the most widely used COVID antibody tests are measuring the right antibody (the primary antibody the immune system uses to target the virus) or if they are measuring a secondary antibody: nytimes.com/2020/07/26/hea…

14. Based on all of this, I think an antibody test is of very limited diagnostic use. It might confirm that we had COVID; it certainly won’t confirm that we didn’t. I am, on the other hand, interested in what it might say from a medical research perspective.

15. If some of my family has antibodies and some don’t, does it correlate with symptoms, disease severity, or length of illness? Or is it random? If none of us have antibodies, could that be a potential explanation for our long illness?

16. And honestly, I’m not laying awake at night wondering if what we had was #C19. We got sick at the exact moment that a global pandemic was breaking out with many of the symptoms that accompany this illness, including some of the weirder ones; we had exposure to a known case;

17. And our long illness and slow recovery has followed the exact same pattern of thousands of people with confirmed COVID infections.

18. I mean sure, there’s always a small chance that it’s not COVID, but that’s kind of akin to saying that there’s a chance the Detroit Red Wings will win the Stanley Cup next year. It’s theoretically possible, but we all know it’s not going to happen.

19. If we need a positive test of some kind to be believed, that's a knowledge-gap problem, not a diagnostic problem. The solution to that problem is greater awareness, not a medical test.

20. Having said that, I once again offer up our bodies to science if anyone is legitimately interested in studying this issue. I'm happy to give blood if it's to contribute to research, rather than to combat #gaslighting.