Towards effective diagnostic assays for COVID-19: a review

Countries globally are affected by the COVID-19 pandemic, with nearly two million cases and 120 000 deaths occurring within 4 months of the discovery of the severe acute respiratory syndrome coronavirus-2 in December 2019 in China. Accurate diagnoses of cases is key in managing the pandemic by identification, isolation and treatment of patients and defining the epidemiology of the virus. By mid-January 2020, a scientist from China published the full genome of the virus, which facilitated the development of accurate molecular diagnostic assays. By the end of January 2020, the WHO, in collaboration with laboratories in Asia, Europe and the USA, published several real-time reverse transcriptase PCR (rtRT-PCR) protocols that allowed identification of cases and development of commercial assays. Clinical investigations facilitated development of accurate case definition and guidance for laboratories on the optimum specimens and procedures for diagnoses. Currently, laboratory-based rtRT-PCR is the recommended test for diagnoses of acute cases to ensure patients can be identified and isolated and to facilitate the public health response. However, due to delays in diagnoses, severe shortage of tests and laboratory capacity, point-of-care molecular or antigen tests are becoming more attractive. Although serological tests are not suitable for diagnoses of acute cases, they are important to define epidemiological questions, including attack rate in the population, and to identify immune individuals. This review aimed to summarise the current available information for diagnoses of cases and to aid laboratories and healthcare workers to select the best assays and procedures.