Covid-19 Diagnostic testing | Dr. Jay Deshmukh

Diagnostic
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Dr Jay Deshmukh MD, FCPS, MNAMS
Diagnostic:- There are two tests available to diagnose this viral infection. These are the Molecular test there Is a lot of apprehensions In public about the I tests to be done to diagnose Covid-19 infection. There are three types of tests available now. These are the RT PCR test, the Rapid Antigen test and the antibody detection in plasma. It Is important to understand the utility of these tests.it is also important to know when these tests are done and in which specific conditions they are Indicated. The advantages In terms of cost, accuracy and time taken to do these tests is important Whether these tests are absolutely accurate In diagnosing Covid-19 Infection Is also an Important consideration.

What the tests available to diagnose Covid-19 infection?

Diagnostic:- There are two tests available to diagnose this viral infection. These are the Molecular test and Antigen test. The Molecular test also called the PCR test that detects the genetic material of the COVID-19 virus using a laboratory technique known as Polymerase Chain Reaction. The Antigen Diagnostic Test rapidly detects certain proteins that are part of the Covid•19 virus. The test results can be ready in a few minutes.

Why have these tests done?

Your doctor may recommend these tests if you have a fever, cough, tiredness, or breathlessness. He may suggest these tests if you have been in close contact with an individual with COVID -19 virus infection or you are at a high risk of complications if you get infected. Certain individuals are considered a high priority for diagnostic testing. This includes health care workers, first responders, or is being cared for in a hospital. If you live in long term care facilities such as nursing homes, prisons, or shelters or are being treated in hospital for other ailments you should at least be tested for the antigen.

How does testing help?

When more Covid-19 tests are available, people who test positive and have symptoms can get care earlier. Contacts can be traced and self-isolation and quarantine started sooner to help stop the spread of the virus. But no Covid-19 test is 100% accurate. It is possible to test negative yet actually be infected. This is a false-negative test. Hence it is vital to follow guidelines formulated by health authorities such as social distancing, until further notice. What the recommendations to mitigate risk from false-negative Covid-19 results? One must strictly adhere to infection control measures including physical distancing, hand hygiene, environmental cleaning and disinfection, and adequate personal protective equipment for health workers. One will have to develop and disseminate accurate and improved RT – PCR tests, serological assays, and assess risk levels before testing. Wherever there is high pretest probability confidence in negative Covid-19 test results should be lower.

What is the significance of these tests?

The RT-PCR test may not be positive in a very early phase of the illness. In situations where the index of suspicion is still high, a repeat RT – PCR testing is indicated. Detection of antibodies in the blood tells you about your body’s response to the virus. This may suggest an infection in the recent past. The present information does not suggest that the presence of antibodies necessarily protects you from infection. You need to do the test for the virus or the rapid antigen test if you have a fever, body ache, cough, breathlessness, or loss of sensation of smell. The antigen and RT PCR test is done by the swab test. The antibodies test is done by a blood test. The antibodies tests tell you whether you have been infected in the past. The virus and antigen test informs you whether you have an infection now.

Do you need to get hospitalized if you test positive?

This decision should be left to the health provider. In case you have mild symptoms like mild fever, mild cough and no breathlessness and are not vomiting with normal oxygen saturation and normal blood pressure, you may have not require in-hospital care. You may be home quarantined and management can be done by your family doctor as per standard guidelines.

What is the significance of antibodies testing!

Antibodies are proteins formed in blood in response to antigen, this could be a viral infection or a bacterial infection. Scientists are not sure how long these antibodies remain in blood after the COVID infection. We are not sure if these antibodies protect us from infection. Doctors do not recommend antibodies testing to know if the person can resume working after the viral infection. Antibodies testing helps us to know how many people in the population have been infected, this helps in epidemiology and community health. Antibody testing may help identify people who can help other individuals with COVID-19 infection so that they can donate their plasma to them.

What is the gold standard test for Covid-19 infection?

A deep nasopharyngeal swab taken by a well-trained technician, collected accurately and tested at a high-quality laboratory and by an accurate method reduces the chances of a false negative result. A false negative response means a test that comes negative in spite of the fact that the infection is present.

What are the advantages of a rapid antigen test?

Diagnostic:- The rapid antigen test against the RT – PCR test, is less expensive and the results are obtained in less than 2 hours. For rapid screening, this is the ideal test for mass detection strategies. Once tested positive, the individual can be quarantined and appropriately treated. Though less accurate than then RT PCR test, it has its own significant importance in mass screenings, low cost, and quick results. The specimen is taken from the nasopharyngeal swab as in RT- PCR test. Testing for Covid-19 infection is quite challenging. The challenges include the cost, time taken, and the accuracy of the results. The results need to be corroborated by an experienced clinician in view of the false-negative tests. Whether the rapid antigen test or the RT – PCR test is advisable depends largely on the decision of the health provider. No test is 100 % accurate.


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Dr Jay Deshmukh is Chief Physician and Director, Sunflower Hospital, Nagpur Honorary Physician to Honorable Governor of Maharashtra and PondicherryCentral. Dr Jay Deshmukh is an M.B.B.S., M.C.P.S., F.C.P.S., M.N.A.M.S., MD From Internal Medicine – Bombay and New Delhi.

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