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February 12, 2021

Weekly line: Did I actually have Covid-19? An antibody test sheds light… sort of.

Daily Briefing
    By Ashley Fuoco Antonelli, senior editor

    Last summer, I came down with an illness that my health care providers and I suspected was Covid-19, despite not having diagnostic test results to prove it. As part of a research project, I recently underwent serology testing to see whether I have antibodies to the novel coronavirus—a process I initially thought would finally give me some definitive answers. But the experience ultimately made me realize something public health experts have been saying since the pandemic's start: For most patients, coronavirus antibody tests really don't mean much of anything. Here's why.

    My suspected case of Covid-19 and why I underwent serology testing

    My suspected case of Covid-19 hit me at the end of June 2020. My illness started with a fever, chills, muscle aches, and nausea. Those symptoms waned quickly, but I rapidly developed new symptoms: fatigue, back and chest pain, difficulty breathing, and a deep cough.

    After seeing health care providers both virtually and in-person, I was diagnosed with a suspected case of Covid-19. And after navigating the difficulty of getting tested for the novel coronavirus in a rural area during the height of America's testing shortage, I awaited my results.

    It took another 12 days of waiting—all while still experiencing fatigue, back and chest pain, difficulty breathing, and a deep cough—to get my results: My coronavirus test was negative.

    But that didn't change my providers' initial diagnosis of suspected Covid-19. My symptoms lined up with Covid-19, and as one of my providers explained, there are accuracy issues with coronavirus tests available in the United States. Because of those issues, receiving a negative test result doesn't necessarily mean you're not infected with the coronavirus. As such, when a nurse called to tell me my coronavirus test result, she also directed me to continue self-isolating until I had at least three consecutive days without symptoms, "just in case."

    So even though I'd received a negative coronavirus test result, I still couldn't be 100% certain I wasn't infected with the virus. And as a result, I also couldn't be certain of whether I had any antibodies to the virus that might possibly protect me against future infection.

    On top of that, some of my symptoms (difficulty breathing, chest pain and tightness, cough, and fatigue) persisted for months, and neither my providers nor I could be sure of what was causing them. Eventually, in late September, those symptoms began to fade. I felt as if I had finally recovered from my illness, though its cause remained a mystery.

    A few months later, I enrolled in a research project focused on Covid-19. As part of the project, I recently underwent serology testing to determine whether I have antibodies to the novel coronavirus, which could indicate that I'd previously been infected by and generated an immune response to the pathogen.

    At first, I was excited to get the serology test's results. I thought the results would finally provide some clarity about what caused my long-lasting illness this past summer.

    A disappointing realization: For many patients, coronavirus antibody tests don't mean much

    As I awaited the results, however, I started thinking back on all the research I've read and reported on regarding coronavirus antibodies, how long those antibodies can last, and what they mean for immunity against reinfection. And, ultimately, I realized something public health experts have been saying throughout the pandemic: Coronavirus antibody test results don't really mean much at all for most patients.

    There are several reasons for that. For one, even if you test positive for coronavirus antibodies and they accurately reflect that you'd been infected by the virus before, researchers still aren't sure whether that guarantees you'll be immune to reinfection going forward. Just last month, the World Health Organization confirmed that reinfection of the novel coronavirus can occur, though it appears to happen rarely. And reinfection may be even more of a risk when faced with emerging new variants of the virus, public health experts have warned.

    Secondly, just because a person tests positive for coronavirus antibodies, that doesn't necessarily mean the virus caused an illness you had in the past. As it stands, researchers still aren't sure exactly how long antibodies to the novel coronavirus last. Because of that, in my case, I can't be sure that any antibodies I may have had against the novel coronavirus were tied to the illness I experienced more than six months ago. And, on the other hand, I can't be sure that any antibodies I may have developed if I was infected with the virus in June still would show up on an antibody test now.

    Further, research has indicated that a significant majority of novel coronavirus infections are asymptomatic, meaning even if you were infected with the virus in the past, it might not have been the cause of any symptoms you experienced. Put another way, it's possible that you may have had a separate illness with symptoms similar to Covid-19 and, at a different point, you were infected with the novel coronavirus but did not experience any symptoms. So in my case, even if I tested positive for coronavirus antibodies, there's no way for me to know whether the virus is what caused my illness last summer, or if I had contracted the novel coronavirus at a different time and simply didn't have any symptoms of the infection.

    All things considered, getting tested for antibodies to the novel coronavirus left me right back where I started. I’m still unaware of what caused my mystery illness last summer. My antibody test came back negative, suggesting I don't currently have any antibodies or natural protection against the virus. But even if my test had come back positive, I still wouldn't know for certain whether I had natural immunity to the virus, so I have no more insight into my body's ability to fend off the novel coronavirus than I had before getting my results.

    That doesn't mean antibody tests are useless

    That's not to say antibody testing isn't useful, however. For some, antibody testing can provide a type of validation for patients who experienced Covid-19 symptoms but lacked access to coronavirus testing or had received negative results. And the tests can be particularly helpful for some Covid-19 long haulers who've struggled to get needed care.

    In addition, antibody tests can play a key role in research, helping scientists to track the novel coronavirus's spread and to inform potential treatments and vaccines for Covid-19.

    But beyond that, Esther Babady, director of the clinical microbiology laboratory at the Memorial Sloan Kettering Cancer Center, told The Atlantic's Katherine Wu that antibody tests don't offer much else, saying that, otherwise, "I can't think of a reason I would want to use an antibody test."

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