BMJ Says Single Antibody Test to Detect COVID-19 May Not Be Accurate

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To fight back the rapidly growing coronavirus disease 2019 (COVID-19), many diagnostic tests have been developed for the detection of the deadly virus. However, to say that a single serology testi can detect antibodies for the novel virus would be wrong as it may not give consistent and accurate information to understand the ongoing COVID-19 outbreak, says a recent paper published in the British Medical Journal (BMJ).

The diagnostic tests that have been developed for early detection of the life-threatening virus have the potential to detect the coronavirus in people two or more weeks after their symptoms started. But, it is still unknown how reliable the tests are for the ones whom symptoms appeared after five weeks or the ones who have milder or no symptoms.

The serologic test which is also known as the antibody test was designed by the Centers for Disease Control and Prevention (CDC). The test is used to detect antibodies that are specific proteins made in response to the deadly coronavirus of which more than 11.2 million people have been reported to be infected globally with over 525,000 fatality cases, according to the data compiled by mixed resources including worldometer and Coronavirus Resource Center_ Johns Hopkins University (JHU).

Source: Worldometer

The positive point of the antibodies test is that it can help a recovered person to have a good immune system but it is still unknown that how long the antibodies will stay in the body to protect the immune system from the infectious viruses.

A Meta-Analysis By Bastos and Colleagues

Bastos and the team did a meta-analysis the included 40 different studies in which there were different serologic testing. The team analyzed 3 types of serologic testing including enzyme-linked immunosorbent assays (ELISAs), which is an immunological attempt to measure antibodies pr antigen. The second test was lateral flow immunoassays (LFIAs), which is an old diagnostic platform that measures liquid samples without any special equipment. The third and the last test was chemiluminescent immunoassays (CLIAs) which referred to like new and advanced immunoassay techniques to detect ultra-high sensitivities.

The team measured sensitivity and specificity for each test and found that only four out of 40 studies involved those patients who got treatment without staying at the hospital. The team also found out that only two studies measured LFIAs at the time of clinical point of care.

Sensitivity vs Specificity

  • Sensitivity is a diagnostic test that can be defined as an approach to detect true disease cases in a diseased population. It is also known as true positive rate.
  • Specificity is a screening test that can be referred to as an approach to detect non-disease cases in a diseased population. It is also known as the true negative rate.

When sensitivity increases, the specificity decreases, and vise versa.

Source: Vet Zone Biostats

As the current paper mentioned that measuring sensitivities from a group of the population can make it harder to check the reliability of the antibody tests during the course of illness. As per Bastos’s analysis, the findings of the ELISAs test were 26.7% during the first week whereas 78.4% rate was measured in the third week.

Way to Control the Poor Performance of A Single Antibody Test

The BMJ suggested making an algorithm that can combine two or more tests for more valid results. BMJ mentioned an example for a better understanding: “In a 5% prevalence setting, screening with one of the more sensitive ELISAs reviewed by Bastos and colleagues (96.0% sensitivity, 99.2% specificity)7 and then using a more specific test (85.0% sensitivity, 100% specificity)8 as the confirmatory test would increase positive predictive value from 55% to 100%”.

The problem still exists that the test would not be reliable if the testing will be done between 14 days after getting infected because the antibodies can be identified from 14 to 21 days after the infection starts.

There is still a better way to diagnose the deadly coronavirus which is currently used by the most of the researchers is a standardized and coordinated approach known as reverse transcription-polymerase chain reaction (RT-PCR), which is one of the most sensitive and reliably quantitative methods for gene expression analysis based on refined analytical methods. This approach is used to combine RT of RNA into DNA. It helps in detecting the negative and positive plasma of COVID-19.

Source: Eurek Alert

There is a still need for more detailed research on serologic testing to find out the remaining questions about how long will the antibody stay in a recovered body and protect the immune system after recovering from the infection.

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