Rapid Antigen and Antibody Microfluidic Immunofluorescence Assays Compared to Culture, PCR, and Laboratory Reference Tests: Performance in a Longitudinal Cohort

Abstract We evaluated the performance of rapid antigen (RAg) and antibody (RAb) microfluidic diagnostics with serial sampling of 71 participants at 6 visits over 2 months following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Rapid tests showed strong agreement with laboratory references (κ Ag} = 81.0%; κ Ab} = 87.8%). RAg showed substantial concordance to both virus growth in culture and PCR positivity 0–5 days since symptom onset (κ Ag-culture} = 60.1% and κ Ag-PCR} = 87.1%). PCR concordance to virus growth in culture was similar (κ PCR-culture} = 70.0%), although agreement between RAg and culture was better overall (κ Ag-culture} = 45.5% vs κ PCR-culture} = 10.0%). Rapid antigen and antibody testing by microfluidic immunofluorescence platform are highly accurate for characterization of acute infection.