Diagnosis of Acute Respiratory Syndrome Coronavirus 2 Infection by Detection of Nucleocapsid Protein

Bo Diao; Kun Wen; Jian Chen; Yueping Liu; Zilin Yuan; Chao Han; Jiahui Chen; Yuxian Pan; Li Chen; Yunjie Dan; Jing Wang; Yongwen Chen; Guohong Deng; Hongwei Zhou; Yuzhang Wu

The fully assembled immunochromatographic strip was then sealed into the plastic cassette ( Fig. 1B) with a sample well and this test device was stored in a dry environment at room temperature and ready for further experiment. With the help of the capillarity of the absorbent pad, sample buffer containing SARS-CoV-2 nucleocapsid protein could be combined by III-conjugated M4 antibody and captured by M1 antibody at the test line, while III-conjugated rabbit IgG could be captured on the control line, resulting in a fluorescent band on the test and control lines, respectively. The fluorescent results will then be read by the immunofluorescence analyzer. Cut-off value was determined by testing 100 nasal swab samples of healthy people and calculated as the mean value of the fluorescence signal plus 5 SD.