Antibody Testing for COVID-19

First independent Australian evaluation of two rapid point-of-care
COVID-19 serology (antibody) Tests.

In response to the COVID-19 pandemic, the Therapeutic Goods Administration (TGA) has expedited the approval (with conditions) of COVID-19 tests including tests intended for laboratory use and those intended for use by specified health professionals at the point of care (POC). Approval was based on the studies manufacturers were able to provide at the time of application.

As part of a Post Market Review the TGA commissioned the Peter Doherty Institute for Infection and Immunity (the Doherty Institute) to carry out a post-market evaluation of these tests. The Doherty Institute has now completed its evaluation of two serology-based POC tests approved by the TGA. These are the Onsite IgM/IgG Rapid Test manufactured by CTK Biotech Inc (USA); and the VivaDiag COVID-19 IgM/IgG Rapid Test manufactured by VivaChek Biotech (Hangzhou) Co Ltd (China).

The results of the Doherty Institute's evaluation show that both manufacturers have claimed a better sensitivity compared to that observed in the Doherty Institute studies. The Doherty Institute found that the sensitivity of the two tests improved with increasing length of time between onset of symptoms in a person and testing. However, even 20 days after onset of symptoms both tests showed sensitivity less than 85%. This means that even three weeks after getting sick, these tests would miss about 15% of people who had been affected by COVID-19. The specificity of these two tests, that is how accurate they were in correctly identifying people who had never been exposed to COVID-19 was approximately 97%. This means that of every 100 people who had never had COVID-19 who were tested about 3 would get a false-positive result.

A number of laboratory-based COVID-19 serology tests are likely to become available over the next few months and these may provide better test performance than the point-of-care tests. However, these will require TGA approval and independent laboratory evaluation before any widespread use.

The Doherty Institute report ends with the following statement; “Overall, our findings are in keeping with recent position statements by the Public Health Laboratory Network (PHLN) and the Royal College of Pathologists Australasia (RCPA) that note that serological assays have limited, if any, role in the diagnosis of acute COVID-19 infection. Our findings strongly suggest that PoCT devices should not be used in the diagnosis of acute COVID-19, and have limited, if any, role in clinical management of individual patients. The role of Point-of-Care tests in population-level serosurveys remains to be seen in the context of other emerging serological tests for SARS-CoV-2”.

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