Make the Most of What We’ve Got and Stay Hopeful for What’s to Come
Guess what. We made it to THURSDAY. Personally, I’m going to treat myself to a change of sweatpants and take some victory laps around my sofa.
BIG PICTURE MEDICAL UPDATE
Today I’m going to talk about TESTING. It’s confusing to hear on the one hand that more testing is ESSENTIAL for safe reopening of the country, but on the other hand that the tests can be UNRELIABLE. So what is the DEAL? There is a lot to break down here, so hike up your pants, adjust your glasses, and tune out your kids’ loud battle for the last remaining Pop-Tart behind you.
Recall that there are TWO types of tests, one for the presence of active virus (or antigen, via a nasal swab) and one for evidence of past infection (antibodies, in blood). Each test has known limitations, but that doesn’t mean they aren’t USEFUL and ESSENTIAL for forward movement back into life.
First, an analogy: You have been working on a 1000-piece puzzle of Brad Pitt’s face (naturally). As you near its completion, you realize you’re missing 100 pieces or more. Which is annoying because you can’t fully make out his chiseled jawline and scruffy chin. But do you QUIT your hard work? Stop gazing at the image? Toss it in the trash? Hell, NO!! You do the best you can with incomplete information and let your brain (blissfully) fill in the contours of his face.
The same thing applies to COVID testing. Just because it’s not perfect doesn’t mean we toss it out. We simply add context.
What’s essential and often misunderstood about COVID testing is the critical importance of layering clinical judgement on the individual patient to appropriately interpret the results.
Let me say that again. The two varieties of COVID tests can fill in pieces of a clinical puzzle but ONLY when we respect their limitations, apply them to the patient’s unique medical situation, and translate results to you and ONLY you. Let’s look at some examples.
Example #1:
My patient Lisa's story was so compelling it was featured on NPR’s All Things Considered. In short, she’s a nurse whose cough, fever, aches, and fatigue in March were highly suspicious for COVID-19. When her nasal swab test came back negative, I didn’t believe it because we knew about the high false negative rate and because her symptoms were classic. Which is why at the time I recommended she behave AS IF she had COVID-19 and then tested her AGAIN when her symptoms persisted. The second time around she tested positive, accurately reflecting our original clinical suspicion. (Note that the false POSITIVE rate of the nasal COVID tests is extremely low.)
PLEASE NOTE: Today’s Washington Post discusses the less-than-ideal newer RAPID test for the presence of active virus. It is made by Abbott Labs and is being used by the White House. It is indeed even less reliable than the nasal swab tests I’ve been using for patients—and is an example of the potential trade-off between test speed and accuracy. Once again, this test (like all others) can be useful but ONLY when not confused with GOSPEL.
Example #2:
My patient with classic spring allergy symptoms (nasal congestion and sore throat) called me last week concerned about her symptoms being from COVID. She had not left her house in a month except for two trips to the grocery store. My PRE-TEST probability (aka my clinical suspicion) of her having COVID-19 was very low, so when her test came back negative, I tended to BELIEVE it, particularly when her symptoms fully resolved after taking Claritin. Did I tell her that she is fully cleared and that I am 100% sure she isn’t carrying the virus? No! Did I tell her that she cannot get COVID at some other time, even today? No! Did I tell her that this is only a snapshot in time? Yes! And to continue to quarantine and keep up the good work? YOU BET! And to wait to re-enter life when DC meets the criteria that our Mayor has wisely set out? YES!
Example #3:
My older patient who had a cough, fever, shortness of breath, and chest pain in March had a positive COVID nasal test on the first try. This patient required short-term hospital care and since then has recovered beautifully. Three weeks after her complete recovery, she came into my lab for antibody testing. We wanted to find out if her immune system had mounted the appropriate response to infection, producing virus-fighting antibody proteins that could potentially protect her from future infection.
At my lab, we use the Abbott antibody test which is considered (not just by me) the best antibody test on the market with a specificity of 99%. Translation: it’s good, with very few (1%) false positives. Note that this is an entirely different test than the rapid test for VIRUS, also made by Abbott, mentioned above.
Her test came back with HIGH LEVELS of antibody. We believe it. Why? Not just because we wanted it to be, but because we CAN. Even if the test WASN’T as accurate as it is, we’d STILL believe the positive test because it MAKES SENSE that someone who tested positive for COVID in March and was as sick as she was would be the VERY PERSON to test positive for antibodies.
I’d like to point out that an article (with an inflammatory title) from today’s New York Times article may make you worry even MORE about antibody tests—especially your own. While I recognize that making decisions about population health can be flawed when tests are not perfect, and I fully agree that the reliability of a test for public health decision-making can only be determined when factoring in the base rate of disease, let’s remind people not to PANIC about testing and instead encourage dialogue with their healthcare provider before making individual medical decisions based on testing alone.
And now! Back to my patient with a robust positive antibody test.
Does this mean she can go lick the floor of Whole Foods? Hug her grandchildren and not worry? Walk around and feel invincible? NO. It means she is carrying a high level of SARS-coV-2 antibody in her body. It means that the positive nasal swab in March was accurate. It means that she LIKELY is immune and that she LIKELY won’t get sick from the very same coronavirus. But—as is true in life—there are no guarantees.
Just like when I wear my seatbelt, drive under the speed limit, and feel confident in my driving ability, am I fully protected from getting in a car accident? No. Is it more likely I won’t? Yes.
It’s all about context. It’s about filtering data appropriately, respecting test limitations, and applying clinical judgment to a particular patient scenario. As much as we’d love a “one size fits all” algorithm for testing, treatment, and overall patient care, it simply doesn’t exist.
And finally, my mental health tip of the day: Make the most of what we’ve got and stay hopeful for what’s to come. (Like completing this puzzle in my mind’s eye.)