The Daily Telegraph reported that a rapid fingerpick COVID-19 antibody test being developed has shown high accuracy.
Prof Paul Hunter, Professor in Medicine, UEA, said:
“Reports that the AbC-19 lateral flow test is 98.6 per cent accurate, if true, are very encouraging. At this stage, however, it is not clear on what set of samples the trial used or what is actually meant by the percentage accuracy. The media report does not contain mention of those key indicators of test accuracy especially the sensitivity and specificity of the test without which it is not possible to be confident that the test is as good as it sounds.
“But the biggest concern for this as with all antibody tests is how long after an infection IgG antibody disappears from the blood. What we do know is that the intensity of the antibody response after infection with COVID-19 depends on the severity of the acute illness. People who are severely ill with viral pneumonia generally have high antibody levels and those that have mild illness have low levels. It is likely that for those with low levels of antibody any test becomes negative quite quickly perhaps within about 3 months. Those with high antibody level may have detectable levels up to about 2 years as was the case with SARS.
“So any claim that the test can tell whether a person has ever been exposed to coronavirus is likely to be suspect. Yes if the test is positive, it would be a very good indication that the person has had a previous COVID-19 infection. However, a negative test may only mean the person has not had an infection in the past 3 months, which is not ever. Also evidence from other human coronaviruses is that immunity after infection is not for life and may not even last till Christmas and so there may not be a direct correlation between presence or absence of antibody and immunity, especially as time passes. If as some research has suggested T-cell immunity may have a role then some people with a negative antibody result may still be immune.
“So, on balance, if these initial reports are correct the test would make an important contribution to our understanding of the spread of COVID-19 and help manage the pandemic in the future. Whether or not the test would be a “game-changer” is uncertain. We will need to wait the publication of the scientific report to be able to make a more valid judgement.”
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