The epidemic curve is shown as the number of patients with coronavirus disease 2019 (COVID-19) admitted at the institution each day. The first case was detected March 13. Serosurvey of staff was initiated from April 22, 2020, to April 30, 2020. Details of the infection prevention measures are depicted below the curve. FFP indicates filtering facepiece; RT-PCR, reverse transcriptase–polymerase chain reaction; TAT, turnaround time.
A, 95% CIs of the odds ratios based on bivariable logistic regression analyses. B, 95% CIs of the odds ratios based on multivariable (with all symptoms included in the model) logistic regression analyses. SARS-CoV-2 indicates severe acute respiratory syndrome coronavirus 2.
aFever could be either subjective or confirmed.
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Steensels D, Oris E, Coninx L, et al. Hospital-Wide SARS-CoV-2 Antibody Screening in 3056 Staff in a Tertiary Center in Belgium. JAMA. 2020;324(2):195–197. doi:10.1001/jama.2020.11160
Belgium has a high burden of coronavirus disease 2019 (COVID-19), especially the region surrounding the Hospital East-Limburg, a tertiary care center.1 Infection prevention measures were instituted in the hospital beginning March 4, 2020, including testing and contact tracing of all symptomatic patients and staff, changes in hospital operations, and provision of personal protective equipment (PPE). The first case was detected March 13 (Figure 1). We investigated the prevalence of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among hospital staff.
From April 22, 2020, to April 30, 2020, all persons who worked at Hospital East-Limburg (including clinical and nonclinical staff and volunteers) were invited for serologic testing. Staff with active symptoms were quarantined and not tested. A single-lane rapid IgG/IgM lateral flow assay directed to the nucleocapsid protein of SARS-CoV-2 (COVID-19 IgG/IgM Rapid Test Cassette; Multi-G) was used. The manufacturer reported high sensitivity and specificity; external validation found performance for IgG comparable to enzyme-linked immunosorbent assay,2 but the specificity and sensitivity for IgM were only 91.3% and 57.9%. Internal validation of the assay using 90 polymerase chain reaction–confirmed cases and 101 historic biobanked samples found a sensitivity of 92.2% and specificity of 97.0% for IgG. Because of inadequate performance, IgM results were excluded. Demographic characteristics and job title were obtained from human resources records. Staff were asked to complete a survey on exposure risks (patient, coworker, and household contact) and symptoms from March 1 (Figure 2). The seroprevalence 95% confidence interval was calculated by the asymptotic method. χ2 Tests were used to compare proportions, t tests to compare age. Odds ratios and 95% CIs were calculated with bivariable logistic regression to assess demographic and job characteristics associated with seroprevalence and with multivariable logistic regression to assess symptoms independently associated with seroprevalence, with all symptoms included as covariates (Figure 2). Missing data were excluded. A 2-sided P < .05 defined statistical significance. Analyses were performed using RStudio version 0.99.902. This study was approved by the local institutional review board, and written informed consent was obtained.
All 4125 staff were invited and 3056 (74%) participated (306 physicians, 1266 nurses, 292 paramedical staff, 555 technical staff, 445 administrative staff, and 192 others, including students and volunteers). At least one-third of those not tested were individuals not at work during the period. Overall, 197 staff (6.4% [95% CI, 5.5%-7.3%]) had IgG antibodies for SARS-CoV-2. Age and sex were not statistically significantly different among staff with or without antibodies (mean age, 39.5 [SD, 13.1] vs 41.3 [SD, 12.4] years; 38/197 [19%] vs 614/2859 [21%] men). Being involved in clinical care, having worked during the lockdown phase, being involved in care for patients with COVID-19, and exposure to COVID-19–positive coworkers were not statistically significantly associated with seroprevalence (Figure 2A). In contrast, having a household contact with suspected or confirmed COVID-19 was associated with antibody positivity (81/593 [13.7%] with household contacts vs 116/2435 [4.8%] without household exposure; P < .001), with an odds ratio of 3.15 (95% CI, 2.33-4.25).
A high proportion of staff mentioned at least 1 prior symptom (2294/3052 [75%]). Of those with antibodies, 30 of 197 (15%) reported no symptoms. Prior anosmia was associated with the presence of antibodies, with an odds ratio of 7.78 (95% CI, 5.22-11.53), as well as fever and cough (Figure 2B).
In this hospital-wide screening study for SARS-CoV-2 antibodies among hospital staff, neither being directly involved in clinical care nor working in a COVID-19 unit increased the odds of being seropositive, while having a suspected COVID-19 household contact did. The high availability of PPE, high standards of infection prevention, and polymerase chain reaction screening in symptomatic staff, coupled with contact tracing and quarantine, might explain a relatively low seroprevalence.3
Limitations of this study include the single-center design and testing of only 74% of staff. Seroconversion may have been missed if testing was too early, especially without IgM results that might reflect more recent infection than IgG.
Quick screening of large cohorts is important to control the pandemic.4 Hospital-wide antibody screening for SARS-CoV-2 can help monitor transmission dynamics and evaluate infection control policies.
Accepted for Publication: June 6, 2020.
Corresponding Author: Deborah Steensels, PharmD, PhD, Department of Laboratory Medicine, Ziekenhuis Oost-Limburg, Schiepse Bos 6, 3600 Genk, Belgium (firstname.lastname@example.org).
Published Online: June 15, 2020. doi:10.1001/jama.2020.11160
Author Contributions: Drs Steensels and Heylen had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Steensels, Oris, Nuyens, Heylen.
Acquisition, analysis, or interpretation of data: Steensels, Oris, Coninx, Delforge, Vermeersch, Heylen.
Drafting of the manuscript: Steensels, Oris, Nuyens, Heylen.
Critical revision of the manuscript for important intellectual content: Oris, Coninx, Delforge, Vermeersch, Heylen.
Statistical analysis: Steensels, Heylen.
Administrative, technical, or material support: Steensels, Oris, Coninx, Nuyens, Delforge, Vermeersch.
Supervision: Steensels, Heylen.
Conflict of Interest Disclosures: None reported.
Additional Information: We thank the hospital board of directors for their financial and organizational support, and nursing director Kurt Surmont, MSc, RN (Ziekenhuis Oost-Limburg), in particular. We thank Toon Schiemsky, MD, for data extraction and Joris Penders, MD, PhD (both at Ziekenhuis Oost-Limburg), for critical revision of the manuscript. None of these individuals received additional compensation beyond salary.
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