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

Background: Frail older persons may have an atypical presentation of coronavirus disease 2019 (COVID-19). The value of real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) testing for identifying severe acute respiratory syndrome coronavirus 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 predict immunisation 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 falls before 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 <0.01, respectively).

Conclusion: This study supports a strategy based on (i) testing residents with typical or unexplained atypical symptoms for an early identification of the first SARS-CoV-2 cases, (ii) rT-PCR testing for identifying COVID-19 residents, (iii) repeated wide-facility testing (including asymptomatic cases) as soon as a resident is tested positive for SARS-CoV-2 and (iv) implementing SARS-CoV-2 infection control measures in rRT-PCR-negative residents when they have unexplained typical or atypical symptoms.