The most recent Cochrane Rapid Review was published Thursday afternoon.
In summary, the rapid review found that antibody tests could have a useful role in detecting if someone has had COVID-19, but that timing is important. The tests were better at detecting COVID-19 in people two or more weeks after their symptoms started, but we do not know how well they work more than five weeks after symptoms started. We do not know if this is true for people who have milder disease or no symptoms, because the studies in the review were mainly done in people who were in hospital. In time, we will learn whether having previously had COVID-19 provides individuals with immunity to future infection.
The researchers also had several concerns about the quality of the studies they found. Studies were small and did not report their results fully. Many papers included multiple samples from the same patients. More than half of the studies were made available before they had been through peer review (publications known as ‘preprints’). In one important UK study the biomarker manufacturers did not approve the identification of the tests that had been evaluated.
Professor Jon Deeks, Professor of Biostatistics and head of the Test Evaluation Research Group at the University of Birmingham, explains:
“We’ve analyzed all available data from around the globe - discovering clear patterns telling us that timing is vital in using these tests. Use them at the wrong time and they don’t work. While these first COVID-19 antibody tests show potential, particularly when used two or three weeks after the onset of symptoms, the data are nearly all from hospitalized patients, so we don’t really know how accurately they identify COVID-19 in people with mild or no symptoms, or tested more than five weeks after symptoms started."
Dr Jac Dinnes, who worked on the review with the University of Birmingham team commented:
“The design, execution and reporting of studies of the accuracy of COVID-19 tests requires considerable improvement. Studies must report data broken down by time since onset of symptoms. Action is needed to ensure that all results of test evaluations are available in the public domain to prevent selective reporting. This is a fast-moving field and we plan to update this review regularly as more studies are published.”
An update of this review is already underway by the authors and will potentially publish later this summer. the update will be more comprehensive in the range of studies it includes, and be more globally relevant.
You can read the full review in the Cochrane Library here or read the press release on cochrane.org.