I got tested for COVID-19 antibodies. Here’s what I learned
Tests sold by private labs can tell you if you’ve been infected, but not whether you’re immune
It was less than 24 hours after my blood had been drawn, but I couldn’t wait to see my test results. I signed in to my online account and saw the words: POSITIVE ABNORMAL. I was thrilled.
It probably sounds strange, but I was relieved to learn that I had been exposed to COVID-19.
This wasn’t a recent exposure. And it wasn’t one of the up-the-nose swab tests that have been conducted, tens of thousands a day, in Ontario as the province faces an alarming second wave.
This was an antibody test, to confirm if the “probable case” of COVID — which in March had me in bed for days and exhausted from simply taking a shower — was actually what I thought it was.
Back then, the swab test, more formally known as the PCR test, was being used to detect active infections but was restricted to high-risk groups, people who had recently travelled. I didn’t qualify. But I had got sick after a dinner with a doctor friend who later tested positive, and I wrote about my experience. There wasn’t a doubt in my mind that I had it, but I never had the piece of paper to prove it.
Since then, there has been lots of interest in antibody tests, which look for the presence of antibodies, proteins used by the immune system to attack bacteria and viruses, in the blood. Interest has come not only from those that didn’t get tested back when they were sick, but also because antibodies typically fight reinfection and hold clues about immunity.
Even U.S. President Donald Trump wondered aloud about his immunity after testing positive for COVID-19.
And with Ontario in the grip of a second wave of new infections, I’m sure I’m not the only one curious about past infection.
Health Canada-approved antibody tests are available, for a price, at private clinics in Ontario. I got mine at Dynacare, a medical laboratory services company, for $70.
But experts told me: don’t assume you’re protected.
Reports of reinfections in recent months suggest a positive antibody test doesn’t mean a guarantee of not contracting COVID-19 again. There has been some lasting immunity for other coronaviruses like SARS (severe acute respiratory syndrome) and MERS (Middle East respiratory syndrome). But the novel coronavirus is only10 months old, and there’s not enough long-term data to make sweeping conclusions.
“For the average person, getting a result and being positive doesn’t necessarily change the game,” said Dr. Zain Chagla, an infectious-disease physician at St. Joseph’s Healthcare in Hamilton.
He’s heard of people who had the worst colds of their lives back in February or March and have since wondered if they could have had COVID.
“Sure, you can go out and spend the $70 and figure that out, for your own personal curiosity, and for your mental health,” he said. But it doesn’t mean you can stop wearing masks or physical distancing, or even that you shouldn’t get tested if you have symptoms again.
In mid-September, the province said antibody tests, sometimes also called serology tests, would be covered under the Ontario Health Insurance Plan, in limited circumstances, where it makes sense for clinical care or public health actions, including for children with a rare inflammatory syndrome that can appear after COVID.
But the tests are available from family doctors and at private clinics for people who don’t qualify under those circumstances and are willing to pay out of pocket.
The executive health-care clinic Medcan has been offering Abbott’s IgG antibody test, approved by Health Canada, to clients since the summer, for almost $300.
Ichor Blood Services, which didn’t respond to a request for further information, advertises the tests for customers in Alberta, Ontario and New Brunswick on its website.
They are also available, as I found out through an email from a reader, at Dynacare.
I went on the website, and that day I was matched to a physician who phoned and asked why I wanted the test. He wrote a prescription and emailed it.
I took that to a small Dynacare lab tucked away in a corner of an office building in downtown Toronto. The polite and efficient women there, dressed in gloves, gowns, masks and face shields, had me in and out within 20 minutes.
Dynacare started offering the test over the summer in Quebec and on Sept. 8 in Ontario for patients who did not meet the criteria for OHIP-covered provincial testing, spokesperson Mark Bernhardt said in an email.
The company runs two of the Health Canada-approved tests: the Roche Cobas ECLIA and then, if a patient’s result is positive, the lab uses the Abbott Architect CMIA to confirm.
The Roche test has a sensitivity (the ability to correctly pick up those who have the antibodies) of100 per cent, and specificity (the ability to pick up those without them) of 99.81 per cent, Bernhardt said. The Abbott test’s sensitivity is 100 per cent, specificity 99.63 per cent, he added.
Dynacare has so far performed a total of 3,259 tests (2,800 in Quebec and 459 in Ontario).
The doctor who had written my prescription also called to follow up, and confirmed that my results don’t make me immune.
“Antibody tests are good for establishing whether someone’s been infected or not,” said Dr. Bruce Mazer, the associate scientific director, strategy, of the national Immunity Task Force, set up by the federal government to co-ordinate research around immunity.
But they don’t tell you when you were infected, or how long they will last. Some tests in the U.S. tell you the levels of antibodies, but mine was just a yes or no.
The tests could be used in group settings such as longterm-care homes, Mazer said, to determine who’s still at risk or, if and when a vaccine arrives, to decide who already has some protection and could be second in line to get the shot.
While there are faster tests available in the U.K. and U.S., some of these are not reliable. All of the Health Canada-approved antibody tests have accuracy rates in the high 90s and are the same ones being used in hospitals across the country, Mazer said.
We make a few different types of antibodies, including IgM, IgA and IgG. IgG is “the most prominent,” he said, and typically appears later, a week or two after infection. These antibodies typically last longest, offering the most protection, and are the type Trump’s doctors say he has, probably because he got a massive dose of them in a treatment.
COVID-19 antibody tests look for the specific antibodies the immune system mounts against the SARS-CoV-2 virus.
For Toronto resident Candice Makhan, who suspects she had COVID in March after contact with a family member who tested positive, it’s been helpful to get tested. Even though she paid out of pocket and both results were negative.
She’s still unable to return to her job at a financial services company, given persistent issues with “sharp stabbing” chest pain that gets worse with any activity, and said she’s been denied short-term disability through her employer without a positive PCR test. She still believes she may have had COVID and that a positive antibody test might strengthen her case.
“It’s kind of endless,” she said. “I’m kind of stuck at this point.”
The 46-year-old Toronto resident turned to both Medcan (which charged about $1,000 for the test and mandatory annual membership) and Ichor (about $200 for someone to come to her home, she said). She may try again with Dynacare given her “livelihood” is stake.
It’s entirely possible for someone to test negative for the antibodies, but still have had the virus. T-cells also play an important part in immunity, Dr. Mazer said.
“What antibodies do is they block the ability to be infected. If you do get infected, antibodies help, but T-cells are what kill the virus, or the cells that are infected,” he said. However, Tcell immunity is less straightforward to test for.
Antibodies also typically fade over time, and “an important part of research is understanding how long these antibodies last and how long they keep people protected,” he added.
A team at the University of Toronto’s Temerty Faculty of Medicine and Sinai Health has been studying just that. They published a new paper Thursday, in Science Immunology, that suggests COVID-19 antibodies can last more than 100 days after infection, in both blood and saliva.
“That’s really good news because that shows we’re making a decent immune response to the virus,” said Jennifer Gommerman, a professor of immunology.
The results “go a little against” some earlier studies that said antibodies from the virus were “crashing,” she added, noting IgM and IgA antibodies “certainly diminished rapidly compared to IgG.”
That’s what you would expect to see, said Anne-Claude Gingras, a senior investigator at the Lunenfeld-Tanenbaum Research Institute, part of Sinai Health System, who also worked on the study. “That’s what the immune system should do.”
Astudy by researchers at Massachusetts General Hospital, published in Science Immunology on the same day as the Toronto paper, also found antibodies stick around for months.
The Toronto team used a brand-new way of testing saliva for antibodies, as well as a tailor-made procedure for finding them in blood, to look at different combinations of antibodies. The method is more sensitive, Gingras said, than the tests I got from Dynacare.
Antibody levels “will drop down at some point,” added Gingras, who is also a professor in the department of molecular genetics at U of T. “The question is when will it drop below a level that would confer protective immunity.”
A handful of cases of reinfection reported around the world have caused some alarm. But for now, there’s not enough data to make any kind of conclusions with just a few isolated cases, said Gingras.
“I think we will hear more about other cases in the next two months, and what is going to be really important is to define, with very clear criteria, whether we know for sure this is a reinfection, and not a persistent infection,” she said.
In some, they are “clearly a reinfection,” as the virus strain was sequenced and found to have different genetic material.
“There’s more and more of those cases, and in most of them, it doesn’t seem like the symptoms are really bad in the second infection, which is what you expect,” she said. “The only thing that it tells you is reinfection is possible; it doesn’t tell you whether it’s likely.”
So in the meantime, given all that we don’t know, are commercial antibody tests just a way to make money?
Chagla said there are precedents for these types of tests, which offer information, but aren’t going to change medical treatment, such as some types of genetic testing.
The main thing is to give people fair and transparent information about exactly what it means and “how to process these results,” he added.
Still, even with all this new knowledge, and the understanding that it’s not a licence to take risks, I feel pretty vindicated with the positive results.
If only, as Chagla said, to satisfy my own curiosity. And honestly, it’s nice to say to all those corona conspiracy believers who trolled me: it wasn’t the flu.