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Potential for False Positive Results with Antigen Tests for Rapid Detection of SARS-CoV-2 – Letter to Clinical Laboratory Staff and Health Care Providers
This unfortunately is not completely surprising. I view any “rapid test” as a test that can get me a result, but may sacrifice sensitivity and specificity to get me that result. This is why we should be reminding clinicians to get confirmatory tests (in this case the RT-PCR test) and aggressively instruct these patients to isolate until it has resulted.
—Andy Little, MD
I’m having flashbacks to epidemiology from med school trying to remember sensitivity and specificity… The reality is that testing in the US is still a disaster. In most places, outpatient tests are taking hours if not days to result, which makes controlling the virus difficult. The antigen test is fast and cheap, ideally used as a screening test so of course confirmatory testing is indicated. We saw this in Ohio where I lived a few months ago when the governor tested positive, then negative. Now, the fact that the FDA put out a warning probably means it’s happening a lot, but not sure what that means other than to get a confirmatory test.
—Andrew Kalnow, DO
Testing and its results are not so straight forward. First, we have to recognize the prevalence of disease as this can affect the positive predictive value of any test. Next, if the sample isn’t taken correctly it can be falsely negative, if patients are not symptomatic it can be falsely negative and if the test results are read too early it can be falsely negative. This has to be balanced with a test that can be falsely positive in situations of reading the test too late and cross-contamination when batch testing. Either way, we know these tests aren’t great, but also that is why performing a confirmatory RT-PCR test within 48 hours is recommended by the CDC.
— Salim R. Rezaie, MD
When assessing the utility of testing, we need to consider pretest probability and what we’re going to do with the results. If a patient has cough, body aches, loss of taste and smell, malaise, and the patient’s spouse already has confirmed COVID, does testing provide any benefit? Similarly, does testing asymptomatic patients provide a benefit? I get the goal of “contact tracing,” but for the past eight months we’ve been doing a crappy job of it and the indications have no scientific basis.
First it was isolating every “contact.” Then it morphed to isolating anyone with whom a COVID patient had spent more than 15 minutes. Elon Musk recently had four tests performed on him using same test, same sampling technique, same lab. Two were positive, two were negative. If we need a piece of paper with a result THAT bad, wouldn’t it be easier and less costly to hire a corona-pup or flip a coin?
—William Sullivan, DO, JD
Scientists hail earwax test for checking stress hormone levels
Finally, a good use for ear wax — checking cortisol levels? I am not sold on this. Although the test is quick, cheap and per the developers effective, a pilot study of 37 patients does not quite do it for me. Making statements about transforming diagnostics and care for millions of people with depression is a bit grandiose at this point in time. How about we prove that this test works first in a larger population?
— Salim R. Rezaie, MD
Any time I hear “earwax,” all I think about is the scene from Shrek where he pulls out a chunk of his earwax, plops it on the table, and lights it to dine by candlelight. The study results are promising, but as with COVID testing, what do we do with the results? Should asymptomatic patient with high long-term ear wax cortisol levels be universally treated for depression? If we can measure ear wax COVID antibodies, that’s a winner. But not everyone has Shrek-level wax in their ears. What is the minimum sample size needed?
—William Sullivan, DO, JD
I am envisioning an unstable septic patient that is not responding to vasopressors asking a nurse to send a stat cerumen test to the lab to determine if we need stress dose steroids! My question is how much wax is needed and does my inappropriate use of q-tips impact testing?
—Andrew Kalnow, DO
The skeptic in me finds this to be unbelievable. How can something my body excretes from my ears, that may be there for a while prior to it being removed an accurate marker of how my thyroid is working? It doesn’t pass the sniff test.
—Andy Little, MD
Experts Worry Antibiotic Resistance may be Worsening During COVID-19
Holy failure to appreciate unintended consequences, Batman! Are these experts who lament antibiotic overprescription during COVID the same experts that chastise physicians who get low patient satisfaction scores from patients who don’t get antibiotics? And are they the same experts who call out emergency departments for not giving pneumonia patients antibiotics within six hours — before doctors could know whether the pneumonia is bacterial or viral? Asking for a friend…
—William Sullivan, DO, JD
So we will have a second pandemic of community-acquired pneumonia following COVID due to antibiotic resistance? In all seriousness, this is a major problem that will continue to plague healthcare and as EM providers, stewardship in many ways starts with us. I think a reasonable approach to patients with COVID or other similar respiratory presentations is to defer initiation of antibiotics to the inpatient team. We know that what we start in the ED will be continued as treatment momentum takes time to reverse. This is not to say patients don’t need early antibiotics, but just be judicious.
—Andrew Kalnow, DO
This is not a surprise, if you prescribe antibiotics like they should be in the water, survival of the fittest would dictate that we would have more resistant bacteria. It’s really simple…antibiotics don’t treat viral conditions, so stop prescribing them for viral conditions.
— Salim R. Rezaie, MD