Did you find this answer helpful? Subscribe to keep up with all things Lifelong Learning.
I have a question about long COVID and antibody tests. A normally healthy and active relative in her 70s was ill with a virus in late November; she took several home tests spaced out a few days (day 3, 5 and 7) and didn't have a PCR until around Day 13. All were negative, but she hasn't been well since then, including having postural hypotension which is being treated and fairly constant nausea and being diagnosed possibly with POTS (she had low blood pressure before this that was being investigated but it didn't affect her quality of life). In spite of the negative tests, I'm wondering if she really did have COVID, and I'd like to ask her doctor to try to rule out that this is long COVID. She is vaccinated and boosted with Moderna; would an antibody test tell us if she had a prior COVID infection (i.e. do they differentiate between antibodies from vaccination vs. antibodies from infection) and if they do, is there a specific antibody test we should ask her doctor to do? Thanks.
The antibody tests offered by various commercial laboratories may differ from each other. Some may provide a test against the virus’ nucleocapsid in addition to the virus’ spike protein. Most labs simply test for antibody against the spike protein. Since the vaccines are made to express the spike protein, the presence of antibody against nucleocapsid could be a clue that a person had a prior “natural” infection with the virus. However, the antibody against nucleocapsid are relatively short-lived, so a negative test result will not give you definitive information on prior infection.
Also, having known prior infection does not necessarily imply that long Covid is the operative cause of the symptoms being experienced. Also, it won’t change the way we would work-up and manage these persistent symptoms. I suggest proceeding with the work up of POTS and other possible metabolic, endocrine, rheumatologic, cardiac, gastrointestinal, or other potential causes of these symptoms. Good luck and sorry that this person is experiencing this constellation of problems.
