Antibody tests for Covid-19 wrong up to half the time, CDC s
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Antibody tests used to determine if people have been infected in the past with Covid-19 might be wrong up to half the time, the US Centers for Disease Control and Prevention said in new guidelines for COVID-19 antibody testing.

• Health officials or health care providers who are using antibody tests need to use the most accurate test they can find and might need to test people twice, the CDC said in the new guidance.

• The new CDC guidelines echo advice from groups such as the University of Minnesota, which cautions against using antibody tests to make policy decisions.

• The higher the sensitivity, the fewer false negatives or false positives a test will give.

• Across populations, tests give more accurate results if the disease being tested for is common in the population. If an infection has only affected a small percentage of people being tested, even a very small margin of error in a test will be magnified.

• The CDC explains why testing can be wrong so often. "For example, in a population where the prevalence is 5%, a test with 90% sensitivity and 95% specificity will yield a positive predictive value of 49%. In other words, less than half of those testing positive will truly have antibodies," the CDC said.

• "Alternatively, the same test in a population with an antibody prevalence exceeding 52% will yield a positive predictive greater than 95%, meaning that less than one in 20 people testing positive will have a false-positive test result."

• Therefore, it's best to use tests with high specificity -- which are unlikely to throw up a lot of false positives -- and in populations where doctors suspect there are many cases," the CDC said.

• The Food and Drug Administration has also cautioned about the accuracy of antibody tests.

Dr. S●●●●●m S●●●●y P●●●●●l and 5 others like this5 shares
Dr. S●●●●●m S●●●●y P●●●●●l
Dr. S●●●●●m S●●●●y P●●●●●l General Medicine
Does this article imply that the test currently we are using has only a 50-50 chance of getting right? This is extremely alarming news! Also,do we have any better alternatives available? Does the US FDA and CDC have a solution to such a critical problem? And thus the logic of lockdown becomes even more favourable.
May 28, 2020Like1