Common Sense

My Life was Turned Upside Down by a COVID-19 Antibody Test

 

Special Issue: AAEM Tales of COVID-19

Author: Matthew C. Holden, MD

 

*As information about COVID-19 testing is rapidly evolving, please excuse data that may not be most up to date at the time of this publication.

I signed in for my shift at the freestanding emergency room I work at and found that in addition to answering the COVID-19 check in questions and getting my temperature taken I would also be getting a finger stick COVID-19 antibody test. I felt fine, had not been ill and had no known recent exposure to a coronavirus patient. I had no cough, sore throat, runny nose, headache, diarrhea, shortness of breath, or body aches. My sense of taste and smell were intact. These questions covered most of the current known symptomatology of the pandemic COVID-19 virus. I knew that there was considerable debate regarding the accuracy of antibody testing and how it should be used but I expected to get a negative antibody test. The two-part test would look for IgM antibodies that develop in the first 7-14 days of the infection. IgG antibodies begin to develop 14 days and peak between 21 and 28 days. They represent the antibodies of the recovery phase of the infection and remain elevated for weeks to months and possibly years. It is unknown whether IgG levels represent immunity to the COVID-19 virus.

Our current best test for active infection is not antibody testing but by real time reverse transcriptase polymerase chain reaction (PCR) test. PCR testing, although not perfect, is what we use to tell us who is infected now. It is the best screening test to help us with contact tracing and quarantine and treatment recommendations. This test identifies viral RNA beginning on or around day one of clinical illness but can remain positive, from current data, for weeks to months even without symptoms. COVID-19 viral RNA are found in nasal, oral or pulmonary tract secretions. They have more recently also been found in feces and sperm. There are multiple ways of obtaining specimen. The most common method involves inserting a nasal swab deep into the nasopharynx and preserving in either a dry or liquid medium. Turnaround times are variable. Some tests take as little as 15 minutes while others may take up to a week. PCR antigen testing is considered the gold standard for diagnostic purposes even though they have variable specificities and sensitivities. Some may only have 80-85% specificity. Sensitivity and false negative rates are also variable due to variable viral loads at different stages of illness, inadequate specimen collection, or problems with transport media or the lab testing itself.

The goal of antibody testing is to tell us what proportion of the population may have been infected and may possibly be immune to COVID-19 in hopes of reopening America safely, but experience thus far has been inconsistent and unreliable. It is not a good test to identify whether someone is acutely infected. By the time IgG and IgM antibody levels are detected, viral levels may already be decreasing or cleared from the system. As of April 21, the FDA had approved four antibody tests. These are all enzyme linked immunosorbent assay (ELISA) tests which can identify whether antibodies are present. The FDA had also allowed at least 50 non approved, mostly lateral flow immunodiffusion tests to be marketed. These are point of care tests that are supposed to be done on site in doctors’ offices or labs but are also sold online for home use similar to point of care pregnancy tests. They utilize small plastic cartridges where a drop of blood or serum is applied to one end, followed by a reagent that mixes with the blood sample and then diffuses up a strip of paper. Antibodies collect along lines as antibodies are deposited and provide a colorimetric reading when positive. A final control line validates the test. Many of the non-approved tests have 20-30% or less sensitivity, limiting their utility. Some of the best tests still have limited specificities. A positive IgM (acute phase) with a negative IgG (recovering phase) should lead to a patient getting a PCR antigen test to see if they have acute COVID1-9. A positive IgM and positive IgG may represent recovery from COVID-19 if it they are true positives, but they still do not rule out the presence of an active viral infection. One danger is that people with false positives may let down their guard and stop avoiding possible exposure and then actually contract COVID-19. Negative IgM antibody test results suggest absence of active illness but it may actually be negative because the patient is in the early and most infectious stage of infection before they start producing a measurable number of antibodies. Again, only PCR testing may provide an answer.

So, I got my finger stick antibody test at the ER and it was positive for IgM. I discussed the findings with my medical director, and he recommended I get a nasal swab PCR antigen study to send out to a lab. He suggested that even though I had no symptoms that I get another doctor to cover the rest of my shift and go home early to await final PCR test results in 2-3 days. I had very mixed emotions. First, I was excited to think that I may have an asymptomatic case of COVID-19. This would make my life as an emergency physician much easier since I could then evaluate and treat patients who may have COVID-19 without worrying if I was going to become infected. And I wouldn’t have to worry about catching the illness through exposure in the community. This is where we all hope to be in a couple of years as the illness spreads through the population and we eventually get immunized with a vaccine. Just maybe I was very very lucky. But I was also apprehensive that if I went home to quarantine with my wife that I might give her a COVID-19 infection that might make her very ill. Another possibility was that I had caught another common cold coronavirus infection from her that was giving me a cross reactive but false positive test. She had a sinus infection and a sore throat for a couple of weeks and had only recently started some antibiotics when it would not go away. To help resolve the dilemma I was able to bring home an antibody test and give her the finger stick test. If she tested positive we could both relax. I presented the test to her as soon as I got home in hopes of being able to avoid a long explanation about possible bad news. “Good news,” I said. “I got one of those antibody tests for you.”

Then the test was negative, and the questions started. Why did I test positive? What if I have it? How can she remain safe?  What does the antibody test mean? Can I get a repeat test somewhere else? Can I go get a nasal swab PCR test with instant results now? How long will we have to wait until we get the test results back from the lab? Can I call the ER tomorrow to see if the results are back and call every day until the results are back? I tried to put myself in her place and be patient and answer every question, every time she asked, in detail. I wore a mask and maintained a healthy separation. I slept in a spare bedroom and tried to stay in a different part of the house. I saw how hard it would be to safely quarantine in the same house with someone infected with COVID-19. As the weekend went on and I continued to feel healthy, I became less hopeful that I had an asymptomatic case. I became more confident that I had a false positive although nothing on the test kit instructions explained what that might be in my case. It was a long, tense weekend. She worried that she might develop COVID-19. I worried about how she might do if she got it. I called for results on Sunday. They were not back. On Monday I got the results phone call from the ER. It was negative. I told my wife I wanted a big hug and a kiss. She said no tongue. We were back to our normal routines in the COVID-19 era.

 


AAEM Tales of COVID-19

AAEM wants you to have a forum to share your thoughts, emotions, opinions, and stories related to the COVID-19 pandemic. Thank you for sharing your ideas with other members so we can get through this crisis together. We will continue to share new stories weekly online and then all stories will appear in the print version of the July/August issue of Common Sense. Submissions are now closed for this special feature.

 

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