The outbreak of new coronavirus disease (COVID-19) has quickly spread all over the world. Real time reverse transcriptase polymerase chain reaction (rRT-PCR) for nucleic acid detection has become the standard method for clinical diagnosis of COVID-19 infection. But these rRT-PCR tests have many inherent limitations, and carry a high false negative rate. It is an urgent to develop a method to accurately identify the vast infected patients and asymptomatic viral carriers from the population. In this article, we present the principle and procedure of developing a colloidal gold immunochromatographic assay (GICA) for rapid detection of COVID-19-specific antibodies. The detection kit can be used to detect immunoglobulin M (IgM) and IgG of COVID-19 in human blood samples within 15 minutes, and to identify different stages of viral infection. Test results can be digitalized using an office scanner and a FiJi software with appropriate confidence interval (CI) setting. Based on analysis from 375 samples, we calculated that overall sensitivity and specificity of the assay were 95.85% and 97.47%, respectively. Compared with rRT-PCR, this assay has many advantages including convenience and rapid detection. The detection kit can be widely used in hospitals, clinics and laboratories for rapid screening of both symptomatic and asymptomatic COVID-19 carriers in large scale.
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