Diagnostic assays for COVID-19: a narrative review

Coronavirus disease 2019 (COVID-19) is a newly emerged infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The number of COVID-19 cases is continuously increasing and no effective drugs or vaccines are currently available. Accurate and efficient diagnostic testing methods are desperately needed for the detection of SARS-CoV-2 and antiviral antibodies in infected individuals. Various assay techniques, including nucleic acid tests [eg, polymerase chain reaction (PCR), reverse transcription-PCR, real-time loop-mediated isothermal amplification, and CRISPR-Cas-based detection], serological tests [eg, immunoglobulin (Ig)A, IgM/G], imaging tests (eg, computed tomography and positron-emission tomography), and nanoparticle-based detections have been reported for COVID-19 diagnosis. This review aims to present the current diagnostic tools for SARS-CoV-2 and their performance characteristics to inform the appropriate selection of diagnostic and surveillance technologies at optimal testing times. We also describe the advantages of detection using combined nucleic acid and imaging tests, or serological testing and point-of-care diagnostics. Developing reliable protein biomarkers targeting the conserved proteins of SARS-CoV-2 rather than IgA, IgM, or IgG would be useful to manage SARS-CoV-2.