COVID-19: What’s in a test?
August 12, 2020

COVID-19: What’s in a test?

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Dr. Yohann White

Chief Innovation officer

Dr. Yohann White is a medical doctor who focuses on vaccines and conditions affecting the immune system.

A patient may get hit on the toe resulting in a break or ‘crack’ in the bone. There is pain when walking or when the doctor presses over that area. However, the break may not show up on an X-ray done right after the injury, but it does not change the fact that the toe is broken; the break may show up on an X-ray done a few days later. Such is the nature of medical tests. A medical test serves to confirm what a doctor believes is the likely condition affecting a patient, or ruling out less likely possibilities. A test result serves as documentation of the patient’s condition, as well as to check whether the patient is getting worse or responding to treatment. Even before a test, based on an individual’s environment, certain symptoms and physical examination, doctors usually have a good picture of the patient’s health. A medical test is part of a comprehensive approach in assessing health status.

Learning from HIV

HIV is a virus – a kind of germ that gets into the body and starts causing damage, sometimes with symptoms, sometimes without. The body puts up a fight against the intruding germ by producing various substances, including antibodies that stick to the virus to try to clear it from the body. Depending on when the person became infected, symptoms, the individual’s situation, and physical signs taken together provide clues on the likelihood of having the virus. Often, there may be no obvious symptoms or signs, but the virus is in the body and may be passed on to someone.

Different types of tests

One of the most widely used tests for HIV is a test for antibodies, made by the body over a period of about three to six months after becoming infected. Because it takes time for these antibodies to be made, antibody tests done close to the time of infection may miss the diagnosis. This is why it is recommended that one gets an HIV test every three to six months. Another type of HIV test looks directly for antigen or a part of the structure of the HIV virus, and these tests can detect HIV sometimes as early as two weeks after infection, even before antibodies are present. Depending on the situation, there are also tests that look for the virus’ genetic material or ‘blueprint’ that the virus uses to build out its structure. For example, we test for the HIV ‘blueprint’ in a baby born to a mother living with HIV, because the mother’s antibodies will also be in the baby and an antibody test would not tell if it is the mother’s or baby’s antibodies. Tests for diagnosing viral infections look directly for parts of the virus or the body’s response to the virus. For more details on each of these tests, read our article on “An Approach to Testing for COVID-19.”

Living with COVID

COVID-19 is caused by severe acute respiratory syndrome SARS-CoV-2 – more widely known as COVID-19. The mainstay of testing for COVID-19 has been by looking for the virus’ blueprint or ‘PCR’* tests, usually with swabs of the back of the nose. The accuracy of tests depends on the timing and the quality of test kits. PCR testing may not be readily available due to manufacturing bottlenecks, export restrictions, staffing requirements, and delays in getting results.

The accuracy of tests depends on the timing and the quality of test kits.

Antibodies against COVID-19 are produced by the body within about one week after becoming infected. Antibody testing is useful in estimating what proportion of the population has been infected, including persons who have cleared the virus but who had not been able to access PCR testing in time. Scientists are also looking into whether the presence of antibodies means protection from being infected again. Additionally, there are tests that detect parts of the COVID-19 structure or antigen soon after infection. COVID-19 is expected to be with us for months and possibly years, requiring a comprehensive approach that uses risk assessment based on the individual’s situation, clinical assessment, and testing. Capacity of our public health facilities, private physicians and laboratories, and academia should be enlisted with coordinated reporting and quality control so that we can protect our citizens in the best way possible.

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