Diagnosis of COVID-19: Considerations, controversies and challenges.

Coronavirus disease 2019 (COVID-19) due to a novel virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic that has resulted in over 1.5 million confirmed cases and close to 100 000 deaths. In the majority of symptomatic cases, COVID-19 results in a mild disease predominantly characterised by upper respiratory tract symptoms. Reverse transcription polymerase chain reaction (RT-PCR) using a nasopharyngeal sample is the mainstay of diagnosis, but there is an ~30% false negative rate early in the disease and in patients with mild disease, and therefore repeat testing may be required. RT-PCR positivity can persist for several days after resolution of symptoms. IgM and IgG antibody responses become positive several days after the onset of symptoms, and robust antibody responses are detectable in the second week of illness. Antibody-based immunoassays have a limited role in the diagnosis of early symptomatic disease. However, their incremental benefit over RT-PCR in the first 2 weeks of illness is currently being clarified in ongoing studies. Such assays may be useful for surveillance purposes. However, their role in potentially selecting individuals who may benefit from vaccination, or as a biomarker identifying persons who could be redeployed into essential employment roles, is being investigated. Rapid antibody-based immunoassays that detect viral antigen in nasopharyngeal samples are being developed and evaluated.

Approaches to laboratory testing for COVID-19

Virologists working in large diagnostic laboratories in South Africa give insights into testing in a pandemic. As the Covid-19 pandemic unfolds, several factors have come to the fore as particularly relevant. Rather than give an overview of current testing guidelines and practices which are prone to change over time, and in any case, for which good reviews are available, the study instead wants to list some of the pertinent issues encountered in South Africa, the African country first and so far worst hit by the pandemic, and some proposed solutions. Clear and up-to-date guidance is needed and must be followed by all role players, including different spheres of government. In South Africa for example, some official governmental recommendations have not been aligned with national Department of Health guidance, and for example, required negative PCR test results before an individual who had Covid-19 was allowed back to their workplace. Such unnecessary requirements serve no purpose but increase the burden on laboratories and interfere with testing of clinically and epidemiologically relevant samples. As the SARS-CoV-2 pandemic spreads, laboratory staff will become infected, too;their infection risk is not exposure to specimens (provided some simple precautions are being followed) but instead to the community and also colleagues. Therefore, the same rules will have to be followed as in all workplaces, including universal wearing of non-medical (cloth) masks, physical distancing, improved hand hygiene, regular cleaning and disinfection of surfaces, etc.