COVID-19 update

The number of COVID-19 cases has increased by 243 as of 27 March 2020, bringing the total number of laboratory confirmed COVID-19 cases to 1170. There has also been 1 death related to COVID-19, in the Western Cape.

Following the growing number of COVID-19 cases in South Africa, the National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS) has received a number of enquiries regarding rapid antibody-based testing kits to diagnose SARS-CoV-2, the causative pathogen for coronavirus disease 2019 (COVID-19).

While we welcome the move and the bold steps taken by companies to increase testing options for SARS-CoV-2, it should be noted currently diagnosis is done by molecular diagnostic tests. These tests detect the SARS-CoV-2 virus itself or genetic material from the virus based on the polymerase chain reaction (PCR) methodology. Testing for SARS-CoV-2 is done in a specialised molecular laboratory, and turn-around times for results are 24-48 hours. The GeneXpert test (Cepheid ®) is a molecular test that will be introduced shortly and has a slightly faster processing time. It is often referred to as a point-of-care test, but still requires specialised machinery and therefore is not suitable for use at the bedside.

The serological (antibody-based) tests are not suitable for the diagnosis of SARS-CoV-2. These tests measure the presence of IgM and IgG antibodies to the virus, which only develop some time after the initial infection once the body has mounted an immune response. As a result, serological tests are not helpful to guide decision making regarding patient management, the need for quarantine, isolation or contact tracing. Furthermore, the serological response to the virus causing COVID-19 (SARS-CoV-2) is not well characterised nor understood, as yet. Typically, antibodies increase later in the course of illness ranging from five to six days after infection or following the onset of symptoms.

While these antibody tests are likely to play an important role in research and surveillance, we wish to communicate that these antibody tests are therefore not currently recommended for the diagnosis of COVID-19.

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