Rapid COVID-19 antibody test is not what we say, scientists warned.


Scientists reported in a new study that rapid finger pricking suggests whether the first person has been infected with SARS-CoV-2 is much less accurate than earlier research.

The ABC-19 rapid test, developed for use by healthcare professionals in the UK and the EU, looks for antibodies against the virus in a small drop of blood by finger prick, and without the need of a special laboratory, only 20 Can show results in minutes. equipment.

The idea is that health care workers can quickly and easily run tests publicly at points of care, and get on-the-spot results on how many people in the community have antibodies against SARS-CoV-2 – a strong The selling point that led the UK government to order one million of test equipment for £ 75 million (around US $ 100 million).

That order was also guided by the positive results of a “comprehensive validation study” funded by the UK-Rapid Test Consortium – a body representing commercial companies, including Abingan Health and Omega Diagnostics, which developed ABC-19 did.

The study, led by researchers at the University of Ulster, Northern Ireland, is publicly available, but is still awaiting peer review.

It was effectively found that the ABC-19 rapid test would yield no false positive results with a specificity of 100 percent. Specificity is the ability to correctly identify a true negative sample rather than giving a false negative.

The Ulster study also found that the test’s sensitivity was 97.7 percent. Sensitivity is the ability to correctly identify a true Affirmative Sample.

Now, however, a new independent study of ABC-19 has found significantly different results in terms of the accuracy of finger prick testing.

A team of scientists from the universities of Bristol, Cambridge and Warwick analyzed blood samples from 2,847 key workers (healthcare workers and first responders) – 268 of whom had previously given a positive PCR result for COVID, compared with 2,579 There was an unknown pre-infection condition.

In addition, they tested samples from 1,995 pre-epidemic blood donors (already known negative from the coronavirus epidemic).

The results of the new study indicate that ABC-19 has a specificity of 97.9 percent (not 100 percent, as claimed by the Ulster study), and its sensitivity is 92.5 percent (based on PCR confirmed cases), but in cases The status of pre-infection can fall to 84.7 percent is completely unknown.

The difference between the two studies likely reflects differences in how the two groups tested the ABC-19 device, but it is being suggested that Ulster research does not provide a clear picture as to the accuracy of the test Can.

“[The Ulster study] Known as positive people who had already tested positive for antibodies to the SARS-CoV-2 protein in three other assays and were selected as known negatives who tested negative in the same three assays , “Two clinical experts, Dependers Gill and Mark Ponsford, write in a commentary article on the findings of the new study.

“The possibility of such a relatively extreme choice of reference standards has underestimated the accuracy of the ABC assay, due to a well-known phenomenon called spectrum bias.”

In further detail, the independent study – led by Ranya Moolchandani, the first author of the UK Field Epidemiology Training Program – was found to be one of five key workers who tested positive with ABC-19, a test positive, in a scenario where tested 10 percent of the population was infected with SARS-CoV-2.

Researchers say none of the tests are ever accurate, but the ABC-19 test reported accuracy is low.

“These new data are very useful on a public health level,” says infectious diseases researcher Eleanor Riley of the University of Edinburgh, who was not involved in the study.

“If we know how many cases the test is missing, and how many are incorrectly making positive calls, we can adjust our population estimates according to the previously determined dose.”

For its part, the UK Department for Health and Social Care (DHSC) insists that the new findings are not a problem for the intended use of ABC-19 – which is under surveillance of pre-infection in the community from the healthcare level, and The current is not diagnosed. COVID-19 infection among members of the public.

“This report states that these tests have been approved for use in surveillance studies that were purchased for them,” it said in a statement.

“They were never intended for this, and were never released for widespread public use and it is misleading and unnecessarily inflammatory to deliberately ignore the fact in the report.”

However, the results from these new revelations can be substantial. There are allegations that the UK government delayed the findings of the new study, and legal proceedings have already begun against the government in relation to the trial.

The findings are stated in BMJ.

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