Which take a look at is finest for COVID-19? – . Well being Weblog

Now that we have been in the COVID-19 pandemic for a few months, the steps we need to take to effectively control the outbreak have become clear: conscientious preventive measures such as hand washing and distancing, comprehensive testing with fast turnaround times, and contact tracing. None of these are easy to maintain over a long period of time. But together, they are our best bets as we wait for better treatments and an effective vaccine.

So what tests should be used?

The many types of tests involved create considerable confusion. Unfortunately, because this novel coronavirus is indeed new and COVID-19 is a new disease, the information about these tests is incomplete and testing options are constantly changing. However, what we do know about tests to diagnose a current infection and tests to show if you have had the virus before.

Diagnostic tests for current infections

If you want to know if you are currently infected with the COVID-19 virus, there are two types of tests: molecular tests and antigen tests.

Molecular tests (also called PCR tests, viral RNA tests, nucleic acid tests)

how is it done? Nasal swabs, throat swabs, and tests of saliva or other body fluids.

Where can you get this test? In a hospital, in a doctor's office, in your car, or even at home.

What is the test looking for? Molecular tests look for genetic material that comes only from the virus.

How long does it take to get results? This depends on the laboratory capacity. Results can be available on the same day, but usually take at least a day or two. During the pandemic, especially recently, delayed turnaround times of up to a week or two have been reported in many places.

What about accuracy? There may be a false negative result, which is a test that says you don't have the virus when you actually have it. The reported false negative rate is only 2% and 37%. The reported rate of false positive results – that is, a test that says you have the virus when you actually don't – is 5% or less.

A molecular test with a deep nasal swab is usually the best option because it will give fewer false negative results than other diagnostic tests or throat swab or saliva samples. However, people who are in the hospital may have other types of samples taken.

You may have heard of pooled testing, which combines multiple samples and performs a molecular test. This could speed up the testing of large numbers of people and reduce the number of tests required.

If a pooled test is negative, the individuals whose samples have been combined will be notified that they have a negative test and individual tests are not required. However, if the pooled sample is positive, then each and every sample taken will be tested to determine who (s) are responsible for the positive pooled result.

This approach can be particularly useful in environments where the number of infections is low and declining and most test results are likely to be negative. In a community where infection appears to be under control and schools and businesses are planned to reopen, collaborative testing of staff and students could be an effective strategy.

Antigen tests

how is it done? A nose or throat swab.

Where can you get these tests? In a hospital or doctor's office (although home tests are likely to be available soon).

What is the test looking for? This test identifies protein fragments (antigens) from the virus.

How long does it take to get results? The technology is similar to a pregnancy test or a rapid strep test, with the results available in minutes.

What about accuracy? The reported false negative rate is up to 50%, which is why antigen testing is not preferred by the FDA as a single test for active infections. However, because antigen testing is faster, cheaper, and requires less complex technology than molecular testing, some experts recommend repetitive antigen testing as a sensible strategy. According to a test manufacturer, the false positive antigen test rate is close to zero. As a result, Ohio Governor Mike DeWine's recent experience of apparently getting a false positive on an antigen test is rare.

Tests for previous infections

Antibody tests (also called serological tests)

how is it done? A blood sample is taken.

Where can you get these tests? At a doctor's office, blood test lab, or hospital.

What is the test looking for? These blood tests identify antibodies that the body's immune system made in response to the infection. While a serological test can't tell you if you have an infection now, it can accurately identify previous infections.

How long does it take to get results? The results are usually available within a few days.

What about accuracy? An antibody test too early can lead to false negative results. This is because it takes a week or two after infection for your immune system to make antibodies. The reported false negative rate is 20%. However, the range of false negative results is between 0% and 30% depending on the study and over the course of the infection.

Research suggests that antibody levels can decline within a few months. A positive antibody test shows you have been exposed to the virus, but it is not yet known whether such results indicate a lack of risk of infection or long-lasting, protective immunity.

The true accuracy of the tests for COVID-19 is uncertain

Unfortunately, it is not exactly clear how accurate these tests are. There are mutliple reasons for this:

• We don't have exact measures of accuracy for these tests – just a few frequently quoted numbers for false negatives or false positives, like those given above. False negative tests offer false certainty and can lead to delayed treatment and relaxed restrictions despite infection. False positives, which are much less likely, can create unjustified fear and require people to be unnecessarily quarantined.
• How carefully a sample is collected and stored can affect its accuracy.
• None of these tests are officially approved by the FDA. They're available because the FDA gave their manufacturers emergency approval. This means that the usual rigorous testing and verification has not been performed and the accuracy results have not been fully published.
• A large and growing number of laboratories and companies offer these tests, so the accuracy may vary. At the time of this writing, there are more than 170 molecular tests, two antigen tests, and 37 antibody tests available.
• All of these tests are new because the virus is new. Without a long track record, accuracy ratings can only be approximate.
• We don't have a definitive "gold standard" test to compare them to.

The final result

Unfortunately, getting a test for COVID-19 can be confusing as options change quickly and tests are marketed by many companies. Despite the current testing limitations, we are fortunate to have reasonably accurate testing available this early in the course of a newly identified virus. Imagine where we would be if it weren't for that.

Still, we need better tests and better access to them. All tests should be rigorously reviewed by the FDA as soon as possible. Finally, generally available testing and short turnaround times for results are essential to achieve effective contact tracing and bring this virus under control.

Follow me on Twitter @RobShmerling

For more information on Coronavirus and COVID-19, please visit . Health Publishing's Coronavirus Resource Center.