Pallett SJC, Rayment M, Patel A, et al. - As a substantial proportion of health-care workers, who constitute a high-risk population for acquisition of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, are not screened in case of suspected infection, researchers sought to determine the performance of point-of-care and laboratory serology assays and their usefulness in late case identification, and to measure SARS-CoV-2 seroprevalence. They performed a prospective multicenter cohort study in two phases including symptomatic health-care workers with mild to moderate symptoms 14 days after onset of COVID-19 symptoms, as per the Public Health England (PHE) case definition. Health-care workers who had not developed PHE-defined COVID-19 symptoms since Dec 1, 2019 were recruited to the asymptomatic cohort. In phase 1, performances of two point-of-care lateral flow serological assays, the Onsite CTK Biotech COVID-19 split IgG/IgM Rapid Test (CTK Bitotech, Poway, CA, USA) and the Encode SARS-CoV-2 split IgM/IgG One Step Rapid Test Device (Zhuhai Encode Medical Engineering, Zhuhai, China), were compared with that of a laboratory immunoassay (EDI Novel Coronavirus COVID-19 IgG ELISA kit [Epitope Diagnostics, San Diego, CA, USA]) in 300 samples from health-care workers and 100 pre-COVID-19 negative control samples. In phase 2 (n = 6,440), they performed serosurveillance among 1,299 (93·4%) of 1,391 health-care workers reporting symptoms, and in a subset of asymptomatic health-care workers (405 [8·0%] of 5,049). Findings revealed both lateral flow serological assays and ELISA to have a good positive predictive value, however, this agreement only occurred if the pretest probability was modified by a strict clinical case definition. Late development of lateral flow serological assay bands would hinder postal procedures and potentially home testing. Among health-care workers, encounter to false-negative results across all assays suggest practicing caution in interpretation of IgG results at this stage; for now, screening is perhaps best carried out in a clinical setting, supported by government advice about physical distancing.