SARS-CoV-2 antigen tests for screening of healthcare workers; experience with over 48,000 combined antigen tests and RT-PCR tests

https://doi.org/10.1016/j.jcv.2022.105326Get rights and content
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Highlights

  • A total of 48,010 paired results of Ag-testing and RT-PCR performed on health care workers were evaluated to determine the diagnostic accuracy of SARS-CoV-2 Ag-tests in diagnosing potentially infectious individuals.

  • Ag-tests showed a good diagnostic accuracy to classify HCWs as potentially infectious or not.

  • Ag-tests correctly identified 45,177 HCWs without SARS-CoV-2, who consequently were all able to work on the day of testing. Thus, the loss of 45,177 working days was prevented during the study period, with a major impact on both health care continuity and hospital finances.

  • To prevent transmission from HCWs to patients while maintaining workforce capacity, Ag-tests are a valuable addition to RT-PCR tests, as they have a quick turnaround time and excellent sensitivity for identifying individuals with high potential for transmission.

Abstract

Background

To prevent spread to patients and co-workers, health care workers (HCWs) infected with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) should quickly be identified. Although real time polymerase chain reaction (RT-PCR) is the gold standard, this test takes several hours, during which a HCW is unable to work. Antigen (Ag) tests may be an efficacious means of screening HCWs since they are easy to perform and provide fast results.

Methods

In this study, 48,010 paired results of Ag-testing and RT-PCR, performed on HCWs between January 2021 and April 2022, were evaluated to determine the diagnostic accuracy of SARS-CoV-2 Ag-tests in diagnosing potentially infectious individuals. This analysis was performed with cycling threshold values (Ct-values) ≤30 and ≤25 as cut-offs.

Results

Respectively 3.1% (n = 1507) and 0.3% (n = 140) of Ag-tests were positive or indeterminate, and thus indicative for SARS-CoV-2 infection. In total, 2479 (5.2%) RT-PCRs were positive, of which 1529 (61.7%) had a Ct-value ≤25 and 402 (16.2%) a Ct-value between 26 and 30. At Ct-value ≤30 as a cut-off, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of Ag-tests were 79.0%, 99.8%, 93.8% and 99.1%, respectively. At Ct-value ≤25, sensitivity further improved to 92.0%, by which the NPV increased to 99.7%.

Conclusions

To prevent transmission from HCWs to patients and co-workers, while maintaining workforce capacity, Ag-tests are a valuable addition to RT-PCR tests, as they have a quick turnaround time and excellent sensitivity for identifying individuals with high potential for transmission.

Keywords

SARS-CoV-2
Antigen test
Hospital management
Infection prevention
Real-time polymerase chain reaction
Health care worker

List of abbreviations

Ag
Antigen
AUC
Area under the curve
CI
Confidence intervals
COVID-19
Coronavirus disease 2019
CT-value
Cycling threshold value
IQR
Interquartile range
HCW
Health care worker
NPV
Negative predictive value
PPE
Personal protection equipment
PPV
Positive predictive value
RT-LAMP
Reverse transcriptase loop-mediated isothermal amplification
RT-PCR
Real-time polymerase chain reaction
SARS-CoV-2
Severe Acute Respiratory Syndrome Coronavirus 2
UMCG
University Medical Center Groningen

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