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We all want to be optimistic, but that shouldn’t stop us from also being critical thinkers when lives are at stake.

A new study out of NYC is, on the surface at least, offering hope to a desperate nation in search of relief from a virus that has stolen both physical and economic security. While optimism is healthy, it can also produce a willingness to avoid facts that threaten to disrupt our desire for good news.

The headline reads: 1 in 5 residents of New York City tested positive for antibodies to SARS-Cov-2. Of course, if these numbers hold true, that would be a positive sign that an overwhelming number of infections are mild-indicating that the mortality rate of the virus may be much lower than previously understood. 20% of people with immunity might also be able to safely return to work with little risk to themselves or others. This would be incredible….but I offer this caution:

Years ago I had a patient. He was struck by a vehicle. His injuries were relatively minor by comparison to the mechanism of his accident, with the exception of his left leg. Puzzlingly, the leg was purple with no pulses and severely painful. Despite the fact that there were no bony injuries, the patient had developed an acute clot secondary to vascular trauma that occluded the main artery feeding his leg. I monitored the cold, pale, painful limb and the patient was booked for the OR. While fetching pain medication, one of his family members excitedly approached me outside the room. “Nurse, come look. His leg is back to normal!” I immediately went to the room with a colleague and found the patient to have a pink, healthy looking, non-painful leg with great pulses all the way down to the foot. My colleague smiled and said “this is great!”. I did not smile. I immediately instructed my colleague to page vascular STAT. I hooked the patient up to an EKG, readied oxygen tubing and drew blood. My colleague returned, “what are you doing? Isn’t this good?” I had only 5 words for him. “Where is the clot now?” Before the physicians could even call me back the patient was taking a downward spiral. Luckily, thanks to a healthy dose of skepticism, interventions were already being done to save his life. The patient lived.

In any scientific field, we are skeptical. We should remain critical of all information if we’re to fully challenge its validity, no matter how much we want it to be true. Lives depend on objectivity.

So, what might be the limitations of this NYC study that says 1 in 5 people may have antibodies that protect against Covid-19?
One that I can spot clearly is the test subject pool. As I understand, Participants were gathered by random sampling at a shopping outlets during a shelter in place. This is important. What do we know about these shoppers?

In my household, and many others, one person is the designated “errand runner”. I am a frontline worker. My exposure is already pretty much guaranteed, so it makes sense for me to be the designated runner in my house. After all, why risk both parents becoming ill. I’m already isolating away from the rest of the members of my household, the grocery store is safer than the hospital I work at in terms of exposure, so I do the shopping. I am many times more likely to have already been exposed (thereby possessing antibodies) than any one of the other 4 members of my household who haven’t left home in 6 weeks. Using me as a representative for the rest of my family is neglecting to get a read on the members that make up 80% of my intimate group. Many, essential workers who have been out and about during the height of the pandemic may have been the test subjects in this sampling. This would drastically skew the percentages, giving a false sampling when applied to the whole- a majority of whom do not have the same exposure/antibody likelihood.

I sincerely hope that we continue to receive information that looks optimistic but it’s important to act (not react) on that information, only after careful vetting of confounding factors -lest we make mistakes that are not easily undone.


https://www.npr.org/sections/coronavirus-live-updates/2020/04/23/842818125/coronavirus-has-infected-a-fifth-of-new-york-city-testing-suggests

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