key: cord-0768775-6vmoupen
authors: Guery, Romain; Cécile, Delaye; Noëlle, Brulé; Virginie, Nael; Louise, Castain; François, Raffi; Decker, Laure De
title: Limited effectiveness of systematic screening by nasopharyngeal RT-PCR of medicalized nursing home staff after a first case of COVID-19 in a resident
date: 2020-05-04
journal: Med Mal Infect
DOI: 10.1016/j.medmal.2020.04.020
sha: be02a399553b283f3f1d21d01b9c2139ce95db57
doc_id: 768775
cord_uid: 6vmoupen

nan

testing for all staff members and residents, even asymptomatic ones, in addition to symptomatic individuals. We report our experience and effectiveness of implementation of these guidelines.

On April 9, 2020, a first case of COVID-19 was suspected in an 80-year-old female resident of a clinical symptoms within 24 hours post-testing, and the last one remained asymptomatic up to 7 days after testing. Implementation of this systematic testing procedure, including administrative organization, nasopharyngeal sampling, symptom-assessment form and follow-up, required the assistance of four nurses, one nursing auxiliary, two medical physicians, and one health executive.

Sample processing and RT-PCR assessment in the virology laboratory required two full-time technicians for two days.

We showed that a prompt point-prevalence survey by systematic nasopharyngeal RT-PCR for SARS- The very low positivity rate of systematic screening of nursing home staff after identification of a COVID-19 case in a resident might be explained by various factors. First, the mean incubation period of COVID-19 is 5 days, and transmission of the virus can occur in the 48 hours before symptom onset [2, 3] . There is therefore a theoretical window period of 3 days during which nasopharyngeal RT-PCR will be negative during the early incubation period, assuming that the transmission risk is correlated with positive SARS-CoV-2 RT-PCR [3] . Second, viral transmission during the incubation period varies between 6% and 44% of cases, which would diminish performances of one-time testing of asymptomatic individuals, even more so if such transmission rate is in the lower range [3] [4] [5] . Third, the survey was conducted four weeks after lockdown and strong decrease of new viral infections in our area, which could also explain the very low positivity rate of RT-PCR. Finally, nasopharyngeal RT-PCR has poor sensitivity, around 70% in symptomatic individuals. Sensitivity is unknown but probably even lower in asymptomatic infected individuals, especially during the incubation period [6] [7] [8] . In conclusion, our study suggests that human resources and cost for systematic screening of all staff members of a medicalized nursing home after diagnosing a first case of COVID-19 in a resident are totally disproportionate according to the limited effectiveness of such point-prevalence survey. Our large screening had limited or even no impact on viral transmission reduction. Whether testing of asymptomatic staff members in medicalized nursing homes should be proposed to better organize COVID-positive and COVID-free dedicated units, in case of large outbreaks, remains to be investigated [9] . A national policy for systematic point testing for SARS-CoV-2 by nasopharyngeal RT-PCR of all staff members of medicalized nursing homes after identifying COVID-19 in a resident should be put on hold.

It should be newly debated when reliable serological tests are available. For the present time, priority should be given to prevention and control recommendations (for all care activities, including during work breaks) and to generalizing the use of face masks (and N95 respirators for invasive acts), as well as rapid testing of all staff members of medicalized nursing homes in case of minor symptoms with immediate isolation and quarantine [10].

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