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Review 4: "Seroprevalence of SARS-COV-2 Antibodies in Scottish Healthcare Workers"

This study reports a greater seroprevalence for antibodies among healthcare workers compared to the general population. Reviewers mentioned concerns over selection of the general population, response bias, and adjusting for potential cross-reactivity with other coronaviruses.

Published onDec 17, 2020
Review 4: "Seroprevalence of SARS-COV-2 Antibodies in Scottish Healthcare Workers"
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key-enterThis Pub is a Review of
Seroprevalence of SARS-COV-2 Antibodies in Scottish Healthcare Workers
Description

Abstract Introduction Healthcare workers are believed to be at increased risk of SARS-CoV-2 infection. The extent of that increased risk compared to the general population and the groups most at risk have not been extensively studied.Methods A prospective observational study of health and social care workers in NHS Tayside (Scotland, UK) from May to September 2020. The Siemens SARS-CoV-2 total antibody assay was used to establish seroprevalence in this cohort. Patients provided clinical information including demographics and workplace information. Controls, matched for age and sex to the general Tayside population, were studied for comparison.Results A total of 2062 health and social care workers were recruited for this study. The participants were predominantly female (81.7%) and 95.2% were white. 299 healthcare workers had a positive antibody test (14.5%). 11 out of 231 control sera tested positive (4.8%). Healthcare workers therefore had an increased likelihood of a positive test (odds ratio 3.4 95% CI 1.85-6.16, p<0.0001). Dentists, healthcare assistants and porters were the job roles most likely to test positive. Those working in front-line roles with COVID-19 patients were more likely to test positive (17.4% vs. 13.4%, p=0.02). 97.1% of patients who had previously tested positive for SARS-CoV-2 by RT-PCR had positive antibodies, compared to 11.8% of individuals with a symptomatic illness who had tested negative. Anosmia was the symptom most associated with the presence of detectable antibodies.Conclusion In this study, healthcare workers were three times more likely to test positive for SARS-CoV-2 than the general population. The seroprevalence data in different populations identified in this study will be useful to protect healthcare staff during future waves of the pandemic.

RR:C19 Evidence Scale rating by reviewer:

  • Potentially informative. The main claims made are not strongly justified by the methods and data, but may yield some insight. The results and conclusions of the study may resemble those from the hypothetical ideal study, but there is substantial room for doubt. Decision-makers should consider this evidence only with a thorough understanding of its weaknesses, alongside other evidence and theory. Decision-makers should not consider this actionable, unless the weaknesses are clearly understood and there is other theory and evidence to further support it.

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Review:

This article by Abo-Leyah et al. reports a higher seroprevalence of SARS-CoV-2 antibodies among healthcare workers in and around Dundee, Scotland compared to the general population.

 The findings appear confirmatory of numerous previous studies of healthcare workers both in the UK and around the world.

 Nonetheless several novel and important observations are made. Notably the finding that Dentistry workers, HCA and Porters are high risk groups alongside Doctors. Previous findings that administrative staff are at similar risk to healthcare practitioners were not reproduced in this study.

 Of note many individuals believed they had had COVID-19, even in the absence of a positive PCR test, but only around one quarter of these individuals were seropositive. However, only ~20% of antibody positive individuals did not believe they had previously been infected, suggesting that true asymptomatic as opposed to paucisymptomatic infections may be rare.

 The main weakness of the study is the statistical analysis. The methodological description is not clear, and it is unclear how covariates have been controlled for. No confidence intervals have been given for the prevalence among different demographic groups or groups of healthcare workers. This is important as some of the more interesting finding are based on quite small numbers (e.g. 50 Dentists, and 27 Porters). Finally, the code for the statistical analysis should be presented as supplementary data.

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