Amarillo Medical Specialists, LLP

There are two main types of COVID testing available 

• Swab testing for the infectious viral particles from your nasal passages.
• Blood testing for antibodies to Coronavirus

To see the "Patient Fact Sheets" for each test, please click on this link.

The status of each test is as follows:

When to use each test:

Nasal Swab / Viral PCR Molecular Test

A swab inserted into your nose will carry the genetic material (RNA)  from the Coronavirus. This RNA is amplified with PCR chemicals over a million times, and then tested for known patterns of the Coronavirus. 

Current practice is to test you with the molecular test IF we have a reason to suspect only Covid 19.  We usually have an adequate supply of the PCR nasal swab tests in stock to test you and have results in less than an hour. 

If a test is needed for travel to another country, this test is accepted by MOST countries. Please check with the country's Covid / travel web site for a list of acceptable tests to be sure. This is considered a "Molecular" test, but is not considered to be a true PCR test.  

Nasal Swab / Viral Antigen Test

A swab inserted into your nose will carry the protein material from the Coronavirus. This reacts with an antibody directed against coronavirus in the test kit.

This test is very useful during flu season, when patients have complaints that may be either Covid or Flu. Our Sofia antigen test kits test for Flu A, Flu B, and Covid 19 at the same time , with only 1 swab. 

Fingerstick Blood Test / Serology IgM IgG

As your body fights off a viral infection , it makes antibodies against the virus. We are currently testing using the Abbott Architect IgG, which has excellent sensitivity (100% at 14 days)  and specificity (99.63%).  This is not like the fingerstick tests which have problems with low specificity. 

The antibodies do not appear in the blood until 3 - 14 days after the start of symptoms. Thus, testing with antibodies alone may miss early infections of less than 14 days. For early infections, you should test with a PCR nasal swab as the primary test. Your doctor may elect do a IgG test in addition, to see if there was a past infection. 

The Covid antibody tests are new, and it is not known yet how long the antibodies persist. Based on the experience with other viruses, the IgG antibodies may last months or years. In the longest report available to date, COVID19 IgG antibodies can last at least 8 weeks. 

Positive results for both IgG and IgM  occur after infection and can be indicative of acute or recent infection. Laboratories within the United States and its territories are required to report all positive results to the appropriate public health authorities.

Per the FDA Emergency Use Authorization,  antibody tests carry the following warning: "Negative antibody results do not preclude SARS-CoV-2 infection and should not be used as the sole basis for patient management decisions. "

THE BOTTOM LINE

There are known issues with both types of tests. The nasal swab has many false negatives due to incomplete sample collection, or if your body is fighting off the virus so well that you aren't shedding viral particles in your nose.   The serology appears to be more sensitive later in the course of disease, however early in the disease process the body may not have produced significant antibodies yet.  Also, there is a concern that other Coronaviruses may cross react and cause a false positive if you have had a previous Coronavirus infection.

We expect that as more experience is gained with these tests, doctors will learn what the best combination of tests are. 

Our current recommendations are:

ACTIVE INFECTION:

Test with either ID Now or Sofia Covid test

RECENT INFECTION MORE THAN 14 DAYS AGO WITH NO CURRENT SYMPTOMS:

Test Serology Only

FREQUENTLY ASKED QUESTIONS

Why test both? 

The nasal swab tests may have up to a 10 - 40% false negative rate. A positive serology test would suggest a  recent onset coronavirus infection, and can be positive as early as 3 days after symptoms start, so it adds more confidence to a negative PCR result. 

Are these tests FDA Approved or Cleared ?

No. None of these tests are approved or cleared by the United States FDA. When there are no FDA-approved or cleared tests available, and other criteria are met, FDA can make tests available under an emergency access mechanism called an Emergency Use Authorization (EUA). The EUA for this test is supported by the Secretary of Health and Human Service’s (HHS’s) declaration that circumstances exist to justify the emergency use of in vitro diagnostics for the detection and/or diagnosis of the virus that causes COVID-19. This EUA will remain in effect (meaning this test can be used) for the duration of the COVID-19 declaration justifying emergency of IVDs, unless it is terminated or revoked by FDA (after which the test may no longer be used).

What does it mean if I have a negative serology blood test result?

A negative test result means that the antibodies to the virus that causes COVID-19 was not found in your sample. However, it is possible for this test to give a negative result that is incorrect (false negative) in some people with COVID-19. A negative result may occur if you are tested early in your illness and your body hasn’t had time to produce antibodies to infection. This means that you could possibly still have COVID-19 even though the test is negative. If this is the case, your healthcare provider will consider the test result together with all other aspects of your medical history (such as symptoms, possible exposures, and geographical location of places you have recently traveled) in deciding how to care for you. It is important that you work with your healthcare provider to help you understand the next steps you should take.

What does it mean if I have a positive serology test result?

The test has several possible results. Depending on the result, it may be more likely that you have COVID-19 and that you may need isolation to avoid spreading the virus to others. Other results may indicate you were infected previously. Your healthcare provider will work with you how to determine how best to care for you based on the test results along with other factors of your medical history, and your symptoms, possible exposures, and geographic location of places you have recently traveled. There is also the small chance that this test can give a positive result that is wrong (a false positive result).

Do I need a negative test to return to work ?

Usually not, the CDC has time based criteria that can be used. Generally you can leave quarantine and go back to work after 10 days have passed with no respiratory symptoms or fever.  We are finding that many people have a positive nasal swab PCR test for weeks after the actual disease has resolved. They are shedding inactive RNA fragments left over from the infection, but those fragments are not infectious. So requiring a negative test is no longer advised for return to work.