key: cord-0826800-h27fk1n5 authors: Vetrugno, G.; La Milia, D. I.; D'Ambrosio, F.; Di Pumpo, M.; Pastorino, R.; Boccia, S.; Ricci, R.; De-Giorgio, F.; Cicconi, M.; Foti, F.; Pascucci, D.; Castrini, F.; Carini, E.; Cambieri, A.; D'Alfonso, M. E.; Capalbo, G.; Fantoni, M.; Moscato, U.; Staiti, D.; De Simone, F. M.; Berloco, F.; Zega, M.; Cattani, P.; Posteraro, B.; Sanguinetti, M.; Laurenti, P. title: COVID-19 seroprevalence among healthcare workers of a large COVID Hospital in Rome reveals strengths and limits of two different serological tests date: 2021-01-09 journal: nan DOI: 10.1101/2021.01.08.21249445 sha: 06342dbb34e0597758d726a10b6dbac4a0757085 doc_id: 826800 cord_uid: h27fk1n5 In several hospitals worldwide, healthcare workers are currently at the forefront against coronavirus disease 2019 (COVID-19). Since Fondazione Policlinico Universitario A. Gemelli (FPG) IRCCS has been enlisted as a COVID hospital, healthcare workers deployed to COVID wards were separated from those with limited or no exposure, whereas administrative staff was destined to work-from-home. Between June 4 and July 3 2020, an investigation was carried out to evaluate seroprevalence of SARS-CoV-2 IgG antibodies among employees of the FPG using point-of-care (POC) and venous blood tests. Sensitivity, specificity and predictive values were determined with reverse-transcription polymerase chain reaction (RT-PCR) on nasal/oropharyngeal swabs as gold standard. Four thousand, seven hundred seventy-seven participants were enrolled. Seroprevalence was 3.66% using the POC test and 1.19% using venous blood test, with a significant difference between the two (p < 0.05). POC sensitivity and specificity were, respectively, 63.64% (95% confidence interval (CI): 62.20% to 65.04%) and 96.64% (95% CI: 96.05% to 97.13%), while those of the venous blood test were, respectively, 78.79% (95% CI: 77.58% to 79.94%) and 99.36% (95% CI: 99.07% to 99.55%). Among low-risk population, point-of-care's predictive values were 58.33% (positive) and 98.23% (negative) whereas venous blood test's were 92.86% (positive) and 98.53% (negative). In conclusion, point-of-care tests have low diagnostic accuracy, while venous blood tests seem to show an overall poor reliability. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint On December 2019, a cluster of a unknown acute respiratory illness occurred in Wuhan city, Hubei 60 Province in China, and rapidly spread to other areas in the following months [1, 2] . The responsible 61 agent was identified by the Chinese Centre for Disease Control and Prevention (CCDC) on January 7 62 2020 and was subsequently named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was later named COVID-19 by the World Health Organization (WHO) [3] . Due to the 64 widespread global transmission of COVID-19 and the high rate of contagiousness, the WHO declared 65 COVID-19 to be a pandemic on March 11 2020 [3] . Early in the SARS-CoV-2 outbreak, several 66 healthcare workers (HCWs) have been infected while providing care to patients with 67 [4, 5, 6] . Identification and isolation of infected and potentially infectious HCWs is indeed relevant to 68 protect them and their families and, besides, may prevent onward transmission to patients and 69 colleagues as well as reduce the risk of healthcare-associated outbreaks [5] . In Italy, COVID-19 cases Limitations include potential false negative results and precarious availability of test materials [18, 19] . Conversely, serological tests have been proposed as an alternative to RT-PCR in cases of acute SARS- CoV-2 infection [20] . They are, in addition, cheaper and easier to implement in laboratory diagnostics 89 . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint for SARS-CoV-2, especially in a point-of-care (POC) format. A clear advantage of these tests over RT-90 PCR is that they can identify individuals previously infected by SARS-CoV-2, even if they never 91 underwent testing while acutely ill [18] . Considering their short time of appearance from the SARS- CoV-2 infection onset, viral specific IgG and IgM antibodies could indicate an ongoing infection [19] . In this regard, population-based sero-epidemiological surveys, especially in healthcare settings, 94 quantifying the proportion of individuals with anti-SARS-CoV-2 antibodies, may be very helpful [21] . The aim of this study was to assess seroprevalence of SARS-CoV-2 specific IgG antibodies among 96 HCWs of the FPG, using serological tests, which rely on venous or capillary blood sampling. The Table 1 ). The study was approved by the FPG Ethics Committee 105 (number ID 3253) and participants signed an informed consent before their inclusion in the study. Both Medical and non-medical HCWs were categorized into two groups whether they had assisted or had 112 not assisted COVID-19 patients, in the period between March 9 2020 (date of the first COVID-19 113 patients in our hospital) and June 4 2020 (date of seroprevalence survey initiation). For predictivity 114 analysis, which requires to consider the prevalence of the studied population, we used AS as further 115 comparison group, because this was a group with low seroprevalence. This is due to the fact that these 116 participants were less exposed to COVID-19 infection than HCWs and many of them had been in 117 work-from-home for two days a week from March 9 2020. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint As above mentioned, participants, which tested positive for SARS-CoV-2 specific antibodies, with at 119 least one of the serological tests used in the study (see below), were sampled for NOS testing [22] 120 within 48 hours after positive serological test results were available. RT-PCR testing on NOS samples 121 was performed using the Seegene Allplex™ 2019-nCoV assay, and a positive result (i.e., a Ct less than 122 40) for at least one of two viral targets (i.e., RdRP and N genes) indicated the presence of SARS-CoV-123 2 RNA. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint because HCWs are a group more exposed to COVID-19 infection risk than the general population. Besides, AS seems to have a lower risk of positivity to SARS-CoV-2, similarly to general population, 150 than most exposed groups, such as HCWs or quarantined persons who had been exposed to SARS- is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. Besides, we also re-estimated the sensitivity and specificity of the POC test using the immunoassay as 161 a reference. The accuracy of the capillary versus the venous test was evaluated with sensitivity, 162 specificity and predictive values with 95% confidence intervals (CI) [18] . All the seroprevalence was 163 stratified for professional category, age and wards in which they worked during the COVID-19 164 emergency. The difference between positivity to one of the serological tests and positivity to the RT-PCR on NOS is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. Table 3 . Pearson's chi-squared test showed a significant difference between the POC and venous blood test is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint 212 . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint Besides, we found a slight difference (but not statistically significant) in the seroprevalence determined 223 by venous blood test between HCWs, who assistance or not assisted in COVID-19 wards: this is in 224 . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint accordance with another study reporting a higher seroprevalence rate than the one reported in our study 225 [27] . The highest seropositivity rates (with venous blood test) among different worker categories were 226 observed for medical doctors. Although this finding is not of immediate interpretation, a possible 227 reason could be their exposure to high risk procedures (i.e., oral intubation, reanimation, clinical 228 examination). Overall, we observed low differences (but not statistically significant) in seropositivity 229 rates between sex and age categories. Our study shows that the specificity was high for venous blood but not for POC test. Conversely, using 231 RT-PCR assay as the diagnostic gold standard, venous blood test sensitivity might meet the criteria for 232 screening tests, unlike POC test sensitivity. NPV were acceptable for both tests, whereas the PPV was 233 acceptable only for the venous blood test, as shown in Table 3 . A systematic review and meta-analysis 234 by Bastos et al. [18] revealed that the current evidence does not support continued use of existing POC 235 tests for COVID-19 serology. On one hand, our study shows a high PPV for venous blood serological 236 testing among a low-risk population (i.e., AS) of hospital staff, on the other hand, this finding may not 237 be the case for a medium/high-risk population (i.e., the entire working community of a COVID 238 hospital). We also observed that, among the subset of participants who tested positive with the venous blood or is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint distinguish HCWs who work in dedicated COVID-19 wards from those with limited or no exposure 255 (i.e., working in non-COVID wards), and allowed work-from-home for AS. We assume that the last 256 group has the same risk of the general population as AS was employed in work-from-home, during the 257 Italian lockdown period. Our study had several limitations. The sample was not drawn randomly and the estimation of the 259 seroprevalence was also subject to other potential sampling bias, due to the voluntarily enrolling Further studies, especially with long-term follow-up, will be needed in the future to assess the value of 271 serological tests, considering their major public health implications. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint Outbreak of pneumonia of unknown etiology in Wuhan, China: 283 The mystery and the miracle Hospitalized Patients With 2019 Novel Coronavirus-Infected Pneumonia in World Health 291 Organization declares Global Emergency: A review of the 2019 Novel Coronavirus (COVID-292 19) Risk to Health Care Workers: A Case Report Screening of 299 healthcare workers for SARS-CoV-2 highlights the role of asymptomatic carriage in COVID-300 19 transmission First 310 experience of COVID-19 screening of health-care workers in England. 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The Lancet ISS Working group Diagnostics and microbiological surveillance of COVID-19: aspects of Evaluation of the 370 EUROIMMUN Anti-SARS-CoV-2 ELISA Assay for detection of IgA and IgG antibodies. 371 Journal of Clinical Virology Carolina Liquid Chemistries Corp. 2019 n-CoV IgG/IgM Rapid Antibody Test Cassette from Primi risultati dell'indagine di sieroprevalenza sul 381 sars-cov-2 First 385 experience of COVID-19 screening of health-care workers in England. The Lancet COVID-19 re-389 infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole 390 genome sequencing Are we underestimating seroprevalence of SARS-CoV-2? 394 . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity.is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprintThe copyright holder for this this version posted January 9, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprintThe copyright holder for this this version posted January 9, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprintThe copyright holder for this this version posted January 9, 2021. ; https://doi.org/10.1101/2021.01.08.21249445 doi: medRxiv preprint