One of the major problems with COVID-19 has been access to tests. At this time, the standard test is a nasal swab requiring a professional lab to evaluate and a turnaround time of 72 hours or longer. It is a PCR Molecular test.
Abbott labs has developed a nasal swab antigen test that can be done in 15 to 30 minutes (BinaxNOW COVID-19 Antigen Card). It requires swabbing the entrance to the nose in both nostrils for about five seconds each by the patient, and then reading the results. We did, in fact, think that we were going to have this test that Abbott labs just released,
BUT, THE PLANS CHANGED
as you might guess during these Covid-19 times, that thought was more just a wish. The US Dept of Health and Human Services bought out all of Abbot’s tests. I will let them explain it:
The second test mentioned above, that Abbott offers to primary care offices, is a test requiring an investment of thousands of dollars for equipment, and then on top of that a per unit cost which depends on scale.
There is another company, Quidel, producing a similar test. Again, hospitals and other large health facilities are getting the first supplies, and it’s also a test that needs an expensive, specialized machine to develop the results. We thought it would be useful to understand some things about these rapid tests, however.
In the Abbott BinaxNOW Covid-19 Antigen test, the antigens are several proteins from the corona virus. The accuracy of a test depends on it’s specificity and sensitivity. A high specificity test will correctly identify people who have the disease (it is specific) and a high sensitivity will correctly identify those who do not have the disease (it is sensitive). In this case, at a specificity of 98.5%, only 1-2 out of 100 tested will have an incorrect positive result. The sensitivity of the test is 97.1%, so it will miss 3 out of 100 who are positive. High sensitivity is the most important number for a deadly, contagious disease.
The best time to do the test is one or two days from the onset of COVID19 symptoms (fever, cough, smell or taste changes, malaise, headaches, etc). If you test for screening purposes, obviously it is good that the test reads negative, but that doesn’t mean the corona virus hasn’t infected you very recently, or that you will not get the disease a day later.
It should be understood that if there is a very high number of people in a population with COVID-19, the predictive value of a positive test is high. When there are few COVID-19 infections in a population, the predictive value of a negative test is more accurate. This is a property of testing that comes from statistical definitions.
Central Family Practice would like to be able to offer these tests, but that isn’t possible at this time. We will continue to evaluate our options as testing evolves.
It needs to be emphasized that having a negative test does not mean that you can let your guard down and forget about social distancing, adequate handwashing, and mask wearing. These measures need to be continued into the near future, and perhaps even a bit longer. Pandemics respond very well to common sense behavior (but at times, people don’t). It looks like Spain has just ordered a state of emergency for the next six months (unless their viral statistics show a major downward trend).
Again, the best time to do this test is soon after symptoms start. Also, if the test is negative, you have to understand that this is just a point in time, and the next point will happen quickly and might include exposure and infection with COVID-19. It’s accuracy could be most trusted in conjunction with quarantining 10 – 14 days before testing.
Just to summarize, if you are positive, you should isolate yourself for ten days from when the symptoms started (or a positive test occurred, if you had no symptoms), and you must be fever free without taking fever reducing medications for 24 hours before returning to usual pandemic activities.
If you have close contact with someone who has documented COVID-19, you should stay at home in quarantine for 14 days after your last contact. Watch for symptoms. Close contact means:
- You were within six feet of someone for a cumulative total of 15 minutes or more
- You provided care at home to someone who is sick with COVID-19
- You had direct physical contact – hugging or kissing
- You shared eating or drinking utensils
- They sneezed, coughed, or somehow got respiratory droplets on you
If you get tested somewhere, ask about their test’s specificity and sensitivity (which needs to be in the high 90’s). Places that are doing testing include: CVS, Remedy Urgent Care, The Health Dept, and large facilities like Austin Regional Clinic and Austin Diagnostic Clinic. If you would like to discuss your situation after the results are back, feel free to make a telephone appointment with us. We have some supportive supplement protocols that may be helpful if you test positive.
The CDC has some excellent information at www.cdc.gov/coronavirus. As you have noticed, the information on corona virus is changing constantly. However, the basics are almost immutable. Below is the Covid Shuffle – to remind you:
ALSO, WE HIGHLY RECOMMEND A FLU SHOT THIS SEASON. Unfortunately our nine month supply has already been depleted and there is no more for us to buy. You can still get your vaccine at a pharmacy or urgent care. Don’t delay! They are going fast!
- Dr. Elliot Trester & Central Family Practice