COVID-19 Testing: False Positives are Definitely a Negative!

Listeners of Talk Ten Tuesdays may remember that earlier this summer, my 89-year-old father tested positive for SARS-CoV-2 via a saliva polymerase chain reaction test, which his caregivers performed as an attempt to catch COVID-19 infections early, on instructions from the state department of health. The results were returned five days later, and I was informed that evening.

The assisted living facility (ALF) went on lockdown, and we all were waiting to see if our loved ones would become symptomatic. On Wednesday, Aug. 26, I received a call from the ALF administrator requesting permission to retest my dad with an intranasal swab test. There were multiple residents and staff whose tests were positive, and they were concerned that the original tests were false positives. That was eight days after the original test.

Three people had been retested already, and the repeat tests were all negative. The administrator expressed frustration at the inability to procure sufficient supplies to do the follow-up nasal or nasopharyngeal testing. The original NovaDx test had been supplied by the government to all long-term care facilities, per the administrator. It seemed unlikely that multiple elderly patients, some of whom likely had some high-risk co-morbid conditions, would all have been asymptomatic.

Up until now, we had been under the impression that the PCR tests have few false positives, and that false negatives are the real issue. These molecular tests are considered to have high specificity (ability to correctly detect uninfected patients, i.e., true negatives – TN/(TN + FP),  but lower sensitivity (ability to detect true positives identifying all infected patients – TP/(TP + FN).

However, the tests had been validated on symptomatic patients. It is problematic to apply tests to situations for which they have not been intended or studied.

A false negative means that a person goes about their business thinking they are not infected or infectious. They can expose other people unknowingly. They can expose an entire football squad or a government office.

The implication of a false positive is different. First, it is insanely difficult to prove that a false positive is actually false, especially in the case of an asymptomatic patient. Cultures for SARS-CoV-2 are not done; the PCR test is considered the gold standard. If there is a lag time of eight days, like in the case of my dad, who’s to say that the first one couldn’t have been a true positive, and the follow-up test was reflective of just the natural clearing of the virus? If we know there are significant numbers of false negatives, how do you know that the second PCR test isn’t the incorrect one?

If a patient is believed to be infected with the coronavirus, they must quarantine and limit their exposure to others. For 14 days, all the residents of the aforementioned ALF were cooped up in their apartments. They ate their meals there, all the activities were on hold again, they didn’t go outside, they didn’t have familial visits. Anyone who has been in contact with a person believed to be positive has to quarantine as well. My father’s healthcare system demands a 28-day lag between the positive test and being able to be seen in person, which leaves him at risk of his other ailments.

If the long-term facility (or a school, for that matter) is doing routine asymptomatic testing, what do they do if quality control issues persist, and there are repeated false positives? Do they undergo serial, perpetual quarantine? Quarantine or isolation has real costs, too. Without socialization, these elderly residents are losing mental faculties. Without school, kids and parents are losing their minds.

What do these nursing homes and assisted living facilities do now with their results? Do they report those patients to the authorities as positives, even if they suspect they are false positives?

Since you can’t really tell who has a false positive, statistics will be skewed. The per-capita death rate is falsely lowered. Inpatient false positives mean the difference between the COVID-19 unit and not. If they don’t really have the disease, they might after being exposed during their hospitalization. Also, remember that Medicare pays an additional 20 percent if there is a positive test result in the chart. Additional resource expenditures and longer hospitalizations may ensue from false positive tests, so perhaps that is not inappropriate.

How did we get here? Tests, similar to the vaccines in development, were hastily thrown into production. Emergency use authorizations, or EUAs, are being handed out like candy on Halloween in 2019.

When this happened to my father, I found an online article from June 18 that uncovered abnormally high numbers of positive results from NovaDx in Texas nursing homes in early June. They were written off as “an isolated incident” involving a specific batch of tubes and transport solution. So why is the government purportedly distributing these tests still?

My dad’s latest test returned negative, and the residents have been released. I am scheduled for my weekly 30-minute visit tomorrow afternoon.

There is room to improve testing, and to improve the tests. To ensure that we know what test results mean in asymptomatic patients. To improve the administration of the tests. We all want the statistics and information surrounding COVID-19 to be accurate and reliable. Testing is one of the key tools in our arsenal to get this pandemic under control.