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The Beginner’s Guide: The Antibody test for COVID-19

The Beginner’s Guide: The Antibody test for COVID-19 

There is a rising concern about the newly established COVID antibody test in London. This has raised curiosity about the accuracy of the test, its significance, and its expectations.

For this article, we will examine the evidence of this test and show you what you need to know. This is a response to the controversy arising from a letter in the BMJ published by some senior academics. This letter conveyed their concerns about antibody testing and its establishment in England.

COVID-19 and the antibody tests

When a person contracts COVID-19, their immune systems produce blood proteins known as antibodies to fight the virus. According to new developments, it is believed that detecting the presence of these antibodies in a person’s blood will determine if they have or had the disease. However, we are not sure of the accuracy of this test, as there are no traces of evidence that proves the method to be 100% accurate for testing both symptomatic and asymptomatic patients.

The antibody test requires blood samples to be collected from the fingertip or vein of the infected person. This test is not the same as the PCR swab, which tests for antigens to prove if a person has a current infection of COVID-19. These antigens are some of the viruses that trigger the body to produce antibodies. These swab tests are not 100% accurate either.

Evidence on antibody tests for COVID-19

We reviewed studies that presented the results for antibody tests for COVID-19 in people who are currently infected, those who have had a previous infection, and those who have never had it. This review covered 54 reports that had test results of about 16,000 samples. The antibodies that were of utmost relevance in these studies were IgA, IgG, and IgM, either singly or combined.

This review boldly revealed that time is significant in the accuracy of the test. According to Professor Jon Deeks, the head of the analysis and professor of Biostatistics, he says that the tests will not work when you use them at the wrong time.

The IgG and IgM antibody test could only detect 30% of COVID-19 patients when it was done between the first to the seventh day of being exposed to the virus. After day 8 to 14 of exposure, the test could detect 70% of the COVID-19 infection. The result rose to 90% from day 15 to 35. From day 35 and above, there was no evidence of accurate results from these tests.

However, there was a low level of falsehood in the results of these tests as they diagnosed 2% of those that were tested positive when they were genuinely negative.

This review showed that there could be different representations based on the IgG and IgM test result for the test performed three weeks after visible symptoms:

If the antibody tests were done on 1000 people and 50 of them (5%) indeed had COVID-19 (just like it would be during a national survey):

  • The result for 58 people will be positive. Out of them, 12 (21%) will have a false-positive result (i.e. 12 people do not have the virus)
  • The result for 942 people will be negative. Out of them, 4 people (0.4%) will have a false negative result (i.e., they indeed had the virus)

If the antibody tests were done for 1000 people in a high-risk setting (health worker, for example) who previously had symptoms and 500 (50%) of them genuinely had COVID-19:

  • There would be 464 positive results for COVID-19, and 7 out of them would be false positive. That means that 2% of the people would not have COVID-19.
  • There would be 536 negative results, and 43 of them would be a false negative. That means that 8% of the people would genuinely have the COVID-19.

From this review, we discovered that the antibody test could be useful for diagnosing COVID-19 for symptomatic patients who tested negative or never had a swab test.

Limitations of this evidence

The studies for this review used data from 25 commercial tests and others that were developed in-house. This is only a small number of antibody tests performed in the world. This made it difficult for the results to be compared with many other tests. Also, most of the tests were carried on results from those admitted to hospitals in China. This means that the data were mostly patients with severe symptoms. Even professor Deeks confirmed this in one of his statements.

Other limitations also appeared to be visible in the quality of the research and the way they were reported.

Other important considerations about antibody tests for COVID-19

Before doing these tests, the health workers should have a solid reason behind their actions and the scale by which they want to undertake it. Also, the limitations and implications of its results should be duly considered. In the aspect of public health, it can be useful to trace the pattern of the spread of the disease and to understand the impact of the quarantine.

Individuals may also find it useful when considering the strange term “immunity passport.” This term generated from some governments, which suggest that having an antibody test can be used to decide if you are fit to receive permission to travel or work, for instance. This, however, depend on the assumption that patients that recovered from COVID-19 are immune to future infections of the virus. There is even no evidence for that. Right now, having a positive antibody test still puts you in a class of those at risk of infection, so you should always observe the safety rules.

This problem is one of those highlighted in the BMJ letter. It pointed out that this test adds little or no solution to the uncertainty of those working in the high-risk setting. The health workers and front-liners are more concerned about the treatment the people with positive antibody tests receive, which is of a disadvantage to them compared to those with negative results or unknown statuses.

The BMJ letter is also concerned about the way the public will have to undergo tests that do not have valid proof of authenticity. From the report, they say that the sole importance for large scale private COVID-19 antibody test London is for research purposes.

You can call Private Blood Tests Clinic London on 020 71830244 to get more information on the Covid-19 antibody test in London.

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