Artist Credit: Ana Maria Botero
We wanted to give you an update on our COVID19 antibody testing program, which we launched this week and have already tested over 100 individuals.
It’s important to remind ourselves how new everything is. The virus only appeared four months ago and we still know so little about how widespread it is in our area, what the typical immune response is and how long immunity will last, whether IgM is a reliable marker of contagiousness, etc… These are all questions which are undergoing intensive research.
In the meantime, we’ve set out to try to answer a few questions in our own community:
- What is the prevalence of people who have been exposed?
- What is the difference in exposure between first responders and the general community?
- How many of those exposed have remained free of symptoms, or had very mild symptoms?
- How accurate is the fingerprick antibody test?
- Does its accuracy depend on how it is “read” or “interpreted”?
Our process has been to contact all of our members and (if you elect to proceed with the fingerprick antibody test) schedule you to come to our office in Prospect. We have again been extremely touched by the large number of you who have offered to contribute towards the testing of our local first responders, and we continue our campaign to raise money to offset the costs of their test kits (THANK YOU!). We also appreciate your patience with our staff and providers as we strive to continue to care for everyone’s healthcare needs while simultaneously testing everyone who wants to be tested.
We will also be sending everyone who has been tested a brief survey that will help us better interpret the results so stay tuned for that.
We hope the information below answers some of your questions about the testing program, and we’ll continue to provide updates as our own understanding evolves.
The Fingerprick Antibody Test for COVID-19:
is a very new test that has not gone through rigorous FDA certification. As such, it is important to realize that while the test may provide useful, actionable information it is not intended to be relied upon as the sole source of information. It is best to combine the information derived from this test with knowledge about symptoms, exposure, and results from follow-up tests.
This antibody test looks for two different types of antibodies in your blood: IgM and IgG. IgM antibodies are detectable roughly 7-21 days after the infection and are the body’s early attempt to fight off the virus. The IgG antibodies develop later and often last in the body for years. These are first detectable around 21 days after infection. The presence of IgG antibodies usually implies that the person has been exposed to the virus but has already recovered or is close to recovery.
What will the testing program of Cloud Medical members and first responders tell us as a community?
A major insight that we are hoping to gain from this initiative will be to help us understand what the prevalence of COVID19 is in Boulder county and what percentage of the population has been exposed to the virus. Thus-far very few people have been tested in our area who do not meet the CDC criteria (which restricts testing only for those with typical symptoms of COVID19). By testing a swath of our our community—of different age groups and other demographics of people with and without symptoms—we’ll get a much better estimate of community-wide exposure. In parallel, we will be doing the same type of testing for higher risk groups of first responders including law enforcement and firefighters.
The major question has to do with prevalence of the virus compared to hospitalizations. We know that nearly 15% of all hospital beds in Colorado are already taken up by patients with COVID19 symptoms. What we don’t know yet is how much of our population has been exposed. If only 1% of the population has been exposed so far, that portends a very different story than if 25% of population has been exposed.
Perhaps the most important result from our initiative may not be what the testing program tells each of us as individuals, but what it tells us about us as a community.
Is it possible to know if I had COVID19 if I don’t get tested?
On an individual level, we know from data from other countries that a large percentage of people exposed and infected with the virus do not know because their symptoms are either atypical, mild, or they had no symptoms whatsoever. Others recall having a viral illness earlier in the year and are left wondering, “was that COVID19?” The antibody test will hopefully help answer that question for many.
What do the preliminary results of Cloud Medical’s antibody testing program suggest?
As of today (4/17/20) we are still dialing in the interpretation of results of these tests and are categorizing results for each antibody into 4 levels based on the intensity of the color of the line: Overtly Positive, Faintly Positive, Very Faintly Positive, and Overtly Negative. According to guidance from the manufacturer, the recommendation was to interpret ANY degree of positivity (even an extremely faint line) as “positive”. But as we begin confirming the fingerprick test with blood draw testing, it is increasingly likely that it may turn out that only the overtly positive lines are in fact “true positives” and the faint ones might be falsely positive.
We also believe that the actual accuracy and reliability of the fingerprick test (as well as its limitations) won’t become fully apparent until we compare a large number of them with blood draw antibody tests. So although we will confidentially report everyone’s results right away, the actual interpretation of what they mean might evolve over the next week or two as more data comes in.
So far everyone who previously tested positive for the virus on PCR (currently the “gold standard” viral genome-based test) had an overtly positive IgG result on the fingerprick test, just as we would expect. So that has been reassuring to see in terms of trustworthiness of the test. A relatively small number of other individuals (who never had a PCR test) have also shown a positive IgG on fingerprick. The incidence of faintly positive IgM results have been quite high thus-far. So we will have to see how both the overtly and faintly positive fingerprick results correlate with antibody blood draws.
We will be reporting your results to you as one of these four gradations of positivity for each antibody, and we recommend anyone who has any degree of positive obtain a confirmation blood draw test, which will be available starting the week of April 20 and which is more accurate. It is possible, or even probable, based on some of the preliminary results we are seeing that some of the faintly positive tests are due to background noise from exposure to other prior coronaviruses (like the one that causes the “common cold”). And that once all of the data is in, it may turn out that only the overtly positive tests are most likely to be true positives and the faint positives will need to be retracted.
How will the Cloud Medical testing program help other communities?
Our goal has always been to think beyond our own neighborhoods. Our initiative is taking measures to precisely track each result, correlate this with a questionnaire based on symptoms and other risk factors, and confirm a significant subset of fingerprick tests with the other test modalities (i.e. blood draw antibody tests, and in some cases PCR). Our sample size of 1000 will be large enough to draw certain conclusions which we hope will add valuable contributions to the vast amount of unknowns that currently exist about the virus—including the answer to the question on everyone’s mind: how accurate are the fingerprick tests, actually?
How does the blood draw antibody test work and how much does it cost?
The blood draw takes an entire vial of blood which allow the lab to quantify the number of antibody molecules in your serum (so both IgM and IgG levels are reported as actual numbers, rather than merely [+] or [-] ). Unfortunately it is pricier than the fingerprick, but our lab partner, US Biotek, has offered us a special wholesale discount of $95 (from their normal price of $150). Receipts can be submitted to your major medical plan for reimbursement. The turnaround for this test is usually 24hrs.
What does it mean if I am negative for both antibodies?
This means that your body does not show evidence that you have been infected by the virus. This is likely because you have not been exposed, or the exposure was too small to result in an activation of your immune system. However, because the antibodies take a while to develop after the initial infection, it is still possible that you were infected in the previous 7-10 days. You should continue with your social distancing, exposure control when receiving packages, hand washing, working from home whenever possible, etc. If you have been practicing good social distancing and have mostly remained at home, it is likely that you are in fact not been exposed.
What does it mean if I am negative and I live with someone who has not been tested?
We recommend that all members of your household continue to shelter at home as much as possible, and if any of you begins to experience cold or flu symptoms, that individual should quarantine within the home (in a spare room, if possible) until the symptoms have resolved for over 1 week.
What if my test shows positive IgM antibodies?
This is not a cause to panic, in fact, since you are not sick enough to be hospitalized, in some ways it is a favorable result because you have likely been exposed to the virus, your body’s immune system is able to manage it, and now you are on your way to becoming immune. We are missing 2 key pieces of data from the clinical evidence that we would love to have. First, we do not know exactly how long IgM can persist, and second, we do not know if IgM is a reliable indicator of contagiousness. We certainly know that a positive PCR nasal swab test definitely indicates that you are contagious but antibodies are different. Since IgM is the “acute antibody”, the presence of IgM does suggest the possibility of transmission, meaning that those who are IgM positive could still potentially transmit the virus to others. We know that IgM can begin to show up as soon as 5 days after exposure, but in many cases takes 10-14 days. Until we know more, we recommend that those with IgM behave as though they are likely contagious and thus take additional precautions to avoid infecting others. Shelter in place, wear a mask whenever leaving the house, and avoid contact with others as much as possible.
Again, if you are only “faintly positive” or “very faintly positive” we suspect that the test is likely detecting antibodies to the common cold virus and not to the virus causing COVID-19. So it is rather likely that those with faint lines will end up being considered “false positives”. But it is still too early to tell for sure. We suggest confirmatory blood-draw antibody test to offer further clarity on antibody status for those who test positive for either IgM or IgG.
In my own personal case, an extremely faint IgM line appeared on my fingerprick test which I immediately confirmed with a blood draw antibody test that came back negative for both IgM and IgG.
What if I have IgM antibodies and others in my household are negative for both antibodies?
This is a common predicament. Our general recommendation here is that the individual with IgM should take extra additional precautions of self-quarantine. This is particularly important for those who live with individuals who are elderly or infirm with other medical conditions. In this case we especially recommend confirmation with blood draw antibody test to gain more insight into your body’s immune response.
What if I have both IgM and IgG antibodies?
This suggests that you are further along in the “recovery phase” and are now also producing convalescent IgG antibodies which are a sign of long term immunity. IgG is very specific against a particular virus, and one of the big questions in research is to find out how long anti-SARS CoV-2 IgG antibodies persist in our blood. We know that in the case of some viruses we maintain detectable levels of anti-viral IgG for decades (which corresponds to protection against being re-infected by that particular virus), whereas for others the IgG levels fade after only a year or so (e.g. influenza).
Another unknown variable is the mutation rate of the virus causing COVID19 which would also affect the duration of immunity. Although many unanswered questions remain, the evidence of IgG in more individuals is an indicator of rising “herd immunity”, which is one of the biggest goals and (we hope) enables us to return to work as soon as possible. Some have suggested the implementation of “immunity passports” for those who are positive for IgG as an indicator of being able to safely return to work. More research is needed, but until we know more, those who still have IgM antibodies should consider themselves to be potentially contagious and continue the restrictions as noted above. We also recommend confirming this result with a follow-up blood-draw antibody test approximately 2 weeks later which would give even more time for IgG levels to rise.
What if I have only IgG antibodies (IgM is negative)?
This is the most favorable outcome and indicates that you are beyond the acute phase and now have the antibodies most consistent with recovery and immunity. We recommend confirmation of this result with a blood-draw antibody test prior to lifting any shelter-in-place restrictions. Such policy recommendations will come from state or federal organizations as more testing occurs and evidence-based guidelines are implemented.
Have a great weekend and put on “Here Comes the Sun” by the Beatles. Long cold lonely winter indeed!
Sending you all lots of positive healing energy!
Your Cloud Medical Team