Antibody tests for diagnosing COVID-19: how relevant are they?

The current standards for detecting active coronavirus disease (COVID-19) infection are molecular tests by reverse transcription polymerase chain reaction, using swabs from the lower or upper respiratory tract. Because of the expertise required and the long turnaround time for the availability of test results, faster and easier point-of-care methods are necessary. The latter may include the detection of antibodies specific to COVID-19. We highlight a recent Cochrane review that assessed the accuracy of antibody tests for diagnosing COVID-19. The review shows that, at present, antibodies have little use in the diagnosis of COVID-19 within the first seven days from onset of symptoms. However, as time progresses, the sensitivity of the antibody tests increases. Antibody tests are more useful in detecting previous COVID-19 infection if used 15 days or more from onset of symptoms. Data presented in the review should be interpreted with caution as most studies (85%) recruited in-hospital patients and 11% recruited suspected COVID-19 patients, while only 4% recruited convalescent patients. This limits generalisability of the results to most settings.