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Quantitative Antigen Test-Based Return-to-Work Strategy for COVID-19-Positive Healthcare Workers: A Single-Center Study from Nikko Medical Center

Year: 2025

Type: article

Abstract: The reclassification of COVID-19 as a Category V infectious disease in Japan on May 8, 2023, shortened isolation periods for healthcare workers (HCP). Although early return-to-work (RTW) is crucial to maintaining hospital operations, it must be balanced against the risk of nosocomial transmission. In this study, we retrospectively analyzed 121 HCP diagnosed with COVID-19 between January 2022 and April 2023, measuring their SARS-CoV-2 antigen levels quantitatively using the LumipulseⓇ SARS-CoV-2 Ag assay. Based on antigen kinetics, we estimated a Day 6 antigen threshold of 1183 pg/mL and set a conservative cutoff at <1200 pg/mL for safe RTW. From May 8, 2023, asymptomatic HCP with antigen levels <1200 pg/mL on Day 6 were allowed to return to work under close monitoring. Between May 8, 2023, and February 23, 2024, 108 of 145 HCP (74.5%) met the RTW criteria and resumed duties without nosocomial transmission. The remaining 37 staff, who either exceeded the threshold or were untested, returned on Day 11, also without incident. Our findings suggest that quantitative antigen testing offers an objective method for determining RTW eligibility and that a threshold of <1200 pg/mL on Day 6 is safe and operationally feasible. This strategy provides a practical balance between minimizing infection risk and sustaining hospital function. Periodic reevaluation of the antigen threshold will be necessary as viral characteristics and vaccination coverage evolve.

Source: Institutional Repositories DataBase (IRDB)