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Review 5: "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 5: "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

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.



The article from Abo-Leyah, Gallant1, Cassidy et al. deals with the level of immunity in the healthcare workers population of a few hospitals in Tayside, a district of Scotland around the city of Dundee and compares it to a ‘control’ population.

The background and justification for the study is really light—it doesn’t provide (even a rapid) literature review or a good description of the added value of their work.

They decided to run an observational survey, which they called a prospective study but it is decidedly not so. It was more a cross-sectional survey with prospective recruitment, since they didn’t collect longitudinal data or follow the participants up over time. There is a clear selection bias in the way they organized the recruitment—participants had to volunteer and register online (no randomization, only people who had access to the advertising could apply). Globally, the methods section is really lacking—no definitions, no sample size calculation, no hypothesis, no justification for the design. They decided to recruit in the global population to have a matched comparable arm, which is a good thing, but the selection was from an hospital blood bank (definitely not a good representation of the global population, clear selection bias again). We don’t have details on the questionnaire or at least type of data collected, apart from blood for serology testing and demographic, which we have to guess by reading the results. A statistical analysis plan is also absent.

The results section is fairly detailed. Tables are clear but are lacking key information (no confidence intervals), and the text is the same way. We find confidence intervals for some statements only. They could have analyzed risk factors associated with level of exposure through seropositivity, through multivariable analysis, but they only report univariate results. They at least provide a slightly deeper analysis of symptoms correlated to seropositivity. The same goes for the use of the matched control population: they don’t perform conditional logistic regression, the only comparison is on the overall seroprevalence, nothing more! What was the point then? This section is really disappointing considering the sample and the design.

Finally, the best part of the article is the discussion. They compare their results to the existing literature, try to explain the differences, and put their results into context. They also provide a few recommendations based on their findings—the need to implement IPC measures in non-medical areas being a fair and clear one.

They address the limitations of the study, but completely forget to mention the clear selection biases of their survey (or any bias, for that matter).

The overall feeling about this article is disappointment. They could have done so much more and so much better. The English is not up to scientific literature standards (bear in mind that I am not a native) and the structure of the paper could definitely be improved.

Therefore, my recommendation for the paper is Major Revise. This does not imply acceptance, but rather indicates that the revised manuscript will likely require re-review by the original Reviewers.

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