A month ago, we thought Crosslands (our adjacent sister community) had its first Covid-19 case. Now, the evidence suggests it probably wasn’t Covid.

Here’s the story, as told in a June 9 memo from CEO Lisa Marsilio: 

“We learned that the one Crosslands resident, who lives in independent living, may not have had the COVID-19 virus. Early May, this resident exhibited all the classic symptoms (fever, cough) which prompted their physician to order a COVID-19 test—which initially came back negative.

Testing protocols, at that time, dictated additional respiratory panel testing and that test came back positive for COVID-19. Thus, our standard cautionary practice was to treat that person in accordance with CDC guidelines for a COVID-19 infection. Through normal contact tracing methods, more individuals were tested, and all came back negative. After the resident’s 14-day quarantine, two repeat tests came back negative and at the same time, an antibody blood test was completed which also came back negative.

While this is good news, Dr. Lawrence indicated that the resident’s test was most likely a false/positive (the resident may have had a type of coronavirus but not necessarily the COVID-19 virus). This demonstrates how fluid testing can be and how false/positive results can occur. As you can imagine that with the process of contact tracing, working through the science, lengthy investigations, and the magnitude of work to maintain the health and safety of our residents, it is vitally important that KCC Administration manage the communications of this nature.”

So, how good is the testing? As I reported back in April, there is a lot of variation in the quality of testing. And it’s not just the antibody testing (with hundreds of brands, often of unknown quality, on the market) but also the nasal-swab PCR tests (which test for the presence of the virus itself, not just antibodies). For example, a recently-published study from Johns Hopkins indicates that PCR tests can miss up to 20% of actual cases when testing is done 8 days after infection (about 3 days after onset of symptoms). And testing that is done a few days earlier or later than that can miss even more cases.

The Crosslands “false positive” test result is less worrisome than “false negative” ones would be. With a false positive, the patient ends up having to quarantine unnecessarily when they don’t actually have the disease (and that’s certainly a problem), but at least they aren’t out spreading the virus when they’ve been told they don’t have it. (That’s the problem with “false negatives”.)

Most of the studies of Covid tests so far have focused on false negatives because of the danger they represent. And it’s hard to find the right population to test for false positives: if someone tests positive, how do you know whether they are actually infected (but without symptoms), or not infected at all (but the test is indicating that they are)? But clearly, there really are false positives—and an unlucky Crosslands resident just experienced one.