Sensitivity of three antibody assays to SARS-CoV-2 nucleocapsid protein in relation to timing since diagnosis

The sensitivity of immunoassay for antibodies to SARS-CoV-2 may decrease over time. We compared three serology assays against SARS-CoV-2 nucleocapsid protein using serum samples of 20 health care workers with a history of mild PCR-confirmed coronavirus disease 2019 (COVID-19) at various timing since diagnosis. Overall, the sensitivity (95% confidence interval) was 95.0 (75.1-99.9), 60.0 (36.1-81.0), and 45.0 (23.1-68.5) for the Roche, Sysmex, and Abbott assays, respectively. The sensitivity of all these assays exceeded 80 for those diagnosed within 6 months, whereas it varied considerably for those diagnosed more than 6 months ago: 88.9 (Roche) versus 0 (Abbott). The present data provide a reference for researchers planning serological studies and interpreting these data. Such assay difference in terms of detection durability can be used, if used in combination, for the estimation of the timing of previously undetected infection.