“…As the BC domains of CBP31-BC interact with any IgG molecules based on different binding affinities [34] , the CBP31-BC-based LFIA is generally suitable for application to samples that do not contain antibodies. However, SARS-CoV-2-specific IgG and IgA appear in nasopharyngeal samples within 2–8 weeks after symptom onset, but not before one week after symptom onset [35] , [36] . Considering that a diagnosis is made early after the appearance of symptoms, we speculated that the developed LFIA could detect SARS-CoV-2 in nasopharyngeal samples without competition between the capture antibody used and other human antibodies on the BC domains.…”