Halting the Spread with Rapid Diagnosis
A critical factor in slowing down the pandemic is the rapid diagnosis of new cases. Nucleic acid amplification tests, such as real-time reverse transcription polymerase chain reaction (RT-PCR), provide the earliest and most accurate diagnosis, but they are costly and time consuming (7). Point-of-care tests, e.g. lateral flow assays for the detection of antibodies are more ideal in the field; however, these tests are of limited value due accuracy issues and the time required to obtain a diagnosis. Rapid antigen detection tests are still undergoing evaluation, and their efficacy is yet to be proven. Figure 3 illustrates various tests being evaluated for COVID-19 and their diagnostic coverage from the acute phase to the convalescent phase.
The sources and accessibility of specimens are also critical for diagnosis. For upper respiratory specimens, the viral Ribonucleic acid yield from nasopharyngeal swabs seems to offer more accurate results than oropharyngeal swabs. The SARS-CoV-2 virus is also detectable in blood, urine and stool; such specimens are not as reliable for diagnosis but are important from the transmission point of view. Proper transport and handling of specimens is necessary to ensure the integrity of the viral RNA and, hence, the accuracy of the diagnostic test. Adherence to biosafety practices is essential, and any testing should be performed in appropriately equipped laboratories by staff trained in the relevant technical and safety procedures (World Health Organization, 2020) (8). Non-propagative diagnostic laboratory work should be conducted at a biosafety level 2 (BSL-2) facility, whereas propagative work, including virus culture and isolation, should be conducted at a containment laboratory with inward directional airflow (BSL-3). Virus isolation is not routine but necessary for characterisation and to support the development of vaccines and other therapeutic agents.