Atypical symptoms, SARS-CoV-2 test results, and immunization rates in 456 residents from eight nursing homes facing a COVID-19 outbreak

International audienceBackground: Frail older persons may have an atypical presentation of coronavirus disease 2019 (COVID-19). The value ofreal-time reverse-transcriptase polymerase chain reaction (rRT-PCR) testing for identifying severe acute respiratory syndromecoronavirus 2 (SARS-CoV-2) nursing homes (NHs) residents is not known. Objective: To determine whether (i) atypical symptoms may predict rRT-PCR results and (ii) rRT-PCR results may predictimmunisation against SARS-CoV-2 in NH residents. Design: A retrospective longitudinal study. Setting: Eight NHs with at least 10 rRT-PCR-positive residents. Subjects: A total of 456 residents. Methods: Typical and atypical symptoms recorded in residents’ files during the 14 days before and after rRT-PCR testing were analysed. Residents underwent blood testing for IgG-SARS-CoV-2 nucleocapsid protein 6 to 8 weeks after testing. Univariate and multivariate analyses compared symptoms and immunisation rates in rRT-PCR-positive and negative residents. Results: A total of 161 residents had a positive rRT-PCR (35.3%), 17.4% of whom were asymptomatic before testing. Temperature >37.8◦C, oxygen saturation <90%, unexplained anorexia, behavioural change, exhaustion, malaise and fallsbefore testing were independent predictors of a further positive rRT-PCR. Among the rRT-PCR-positive residents, 95.2% developed SARS-CoV-2 antibodies vs 7.6% in the rRT-PCR-negative residents. Among the residents with a negative rRT-PCR, those who developed SARS-CoV-2 antibodies more often had typical or atypical symptoms (P=0.02 and