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COVID-19

The Process of Coronavirus Detection

This article will be examining and summarizing two forms of Coronavirus detection. This information was gathered and analyzed using the CDC’s official website and other trusted webpages. This information was analyzed in a way for the average person to understand.

I preface by giving a warning that the FDA has seen multiple unauthorized testing kits for COVID-19 sold online. These kits can conclude to be hazardous and you should always just go to your local testing site.

The most common testing method in the United States consists of a healthcare worker using a long swab to grab a sample which will then be sent out for testing. Other countries may use blood samples. Both Blood and the swab sample take up to a week for results.

Tests using Q-tips are known as molecular tests. These molecular tests detect active infection. In other words, it checks for the presence of coronavirus. The tests are run through what is known as Real-time reverse-transcription polymerase chain reaction, or rRT-PCR. Currently, laboratories are required to have a positive result from the rRT-PCR assay in at least two specific genomic targets (an assay is essentially an analytic procedure completed in laboratories). Laboratories check for a single positive target with sequencing of a second target to get confirmation that coronavirus is present in the sample. 

Overall, the success of the molecular test relies on many factors. That is why the CDC has strict guidelines for how to handle and work with molecular test samples. To get a more accurate result scientists are recommended to get multiple samples. These samples are various types of respiratory samples, serum, and stool specimens. A single negative result for coronavirus does not result in the guarantee that a person does not have coronavirus, so they are put “under investigation”.  This test only takes a couple of hours to run.

Tests using blood samples are called a serology test. These tests look for previous infection or antibodies for coronavirus. The presence of these antibodies tells the scientists that person had the virus and developed an immune response to it. These tests are not flawlessly accurate but scientists are working to make them precise, using information on how the virus is transmitted. The CDC requires a two phase approach for these serology tests. Phase one uses two screening tests while phase two uses one confirmatory test to detect coronavirus antibodies. 

Phase one includes the enzyme-linked immunosorbent assay and the microneutralization assay. The enzyme-linked immunosorbent assay is also known as ELISA. This test is used to discover whether there is concentration of specific antibodies. The microneutralization assay is used to measure antibodies that can neutralize the virus. This test takes a minimum of 5 days to find results.

The following are how the CDC determines the results of the serology tests:

  • If a clinical sample is positive by either ELISA, or positive by micro neutralization, the specimen is determined to be confirmed positive.
  • If a clinical sample is positive by both ELISAs, and negative by micro neutralization, the sample is determined to be indeterminate.
  • If a clinical sample is positive by only one ELISA, and negative by micro neutralization, the sample is determined to be negative.
  • If a clinical sample is negative by both ELISAS, the sample is determined negative.

The differences between the two tests are, a serological test can detect antibodies even if a patient has recovered, whereas a molecular test can detect the virus only if the person is currently infected. Both the molecular tests and the serological tests are risk free, but you may feel some discomfort or pain while someone is getting a sample.

The tests I did not discuss are Nasal aspirate, Tracheal aspirate, and the Sputum Test. These tests are less common, but you are encouraged to research them.

Some hospitals and various agencies have set up Drive-through coronavirus testing centers. Be sure to do your own research on these.

Rapid PCR tests are currently being developed. Scientists are working very hard to find a more convenient and less cost effective way to detect coronavirus. Currently, the coronavirus tests developed by the CDC, Washington, and New York are PCR tests.

Some good information to know:

  1. COVID-19 tests are very new and false negatives can occur. 
  2. At home tests are to be used with precaution as the quality of the specimen is largely unknown.