The recent Cochrane review found that testing antibodies for COVID-19 would only yield accurate results if done under precise timing. Researchers have found that the optimum time for testing would be three to four weeks after having the disease.
Testing too early or late would give off unreliable results, the experts say. Furthermore, they found that testing within two weeks would produce an accuracy rate below 70 percent. On the other hand, there is not enough data to determine how definite results would be when testing after five weeks.
Moreover, it is unclear whether the antibody tests would work on non-hospital patients and those with mild coronavirus cases. Researchers admit their uncertainty on the tests for patients with mild symptoms as most tests have been carried out on badly ill and admitted patients.
One scientist said none of the antibody tests currently available on the market are competent enough to be used outside hospital settings.
The independent review led by scientists from the Cochrane Institute and the University of Birmingham studied data from 54 antibody test studies on 16,000 blood samples.
According to Professor Jon Deeks from the University of Birmingham, and one of the scientists behind the international review, they've discovered an apparent pattern indicating that timing is vital when using the antibody tests. If used at the wrong time, they won't work, he says.
The review found that only seven out of ten COVID-positive individuals would receive a positive result if the antibody blood tests were taken within two weeks of developing symptoms.
Between 15 and 35 days after experiencing symptoms, the review found that the accuracy increased to more than 90 percent on average. As for those who tested after having symptoms 35 days earlier, the review found that there were insufficient studies to estimate how accurate results were during the period.
For patients who had symptoms 35 days ago or longer, there were 'insufficient studies' to estimate how well the tests could work. Moreover, they said there was not enough data available to determine whether lab-based tests were better than hand-held ones.
Too Much Uncertainty About Antibody Tests
Scientists still aren't 100 percent sure about antibody tests and their accuracy. In traditional medicine, the existence of antibodies would mean that someone is almost guaranteed not to get sick with the same infection twice. However, with COVID-19 survivors, there is still no definitive proof that they are indeed immune.
The review mentioned that the scientists do not know how well the tests would work for those with asymptomatic or mild patients. This was because most studies were done mainly in people who were severely ill and hospitalized.
According to Dr. Jac Dinnes, a Birmingham researcher who worked on the review, the studies that had been done on antibody tests so far were not of high quality. She mentioned that the execution, design, and reporting of the studies on the accuracy of COVID-19 tests needs further improvement.
Antibody Testing Still Helpful Even if Accuracy is Doubtful
According to experts, there is already enough data suggesting that antibody tests can be used to scrutinize the number of people who have been affected. In the UK, the tests are used for NHS staff. The tests determine which ones have already had the virus and therefore, can be transferred to "clean wards."
Moreover, it is also being used for population surveillance to check how many members of the public have already had the illness. Both the Public Health England and Office for National Statistics are using antibody tests for this purpose and have already tested tens of thousands of individuals to date.
