Comparing the diagnostic accuracy of point-of-care lateral flow antigen testing for SARS-CoV-2 with RT-PCR in primary care (REAP-2)

Werner Leber; Oliver Lammel; Andrea Siebenhofer; Monika Redlberger-Fritz; Jasmina Panovska-Griffiths; Thomas Czypionka

doi:10.1016/j.eclinm.2021.101011

Comparing the diagnostic accuracy of point-of-care lateral flow antigen testing for SARS-CoV-2 with RT-PCR in primary care (REAP-2)

EClinicalMedicine. 2021 Aug:38:101011. doi: 10.1016/j.eclinm.2021.101011. Epub 2021 Jul 13.

Authors

Werner Leber¹, Oliver Lammel², Andrea Siebenhofer^{3

4}, Monika Redlberger-Fritz⁵, Jasmina Panovska-Griffiths^{6

7

8}, Thomas Czypionka^{9

10}

Affiliations

¹ Centre for Primary Care, Wolfson Institute of Population Health, Barts School of Medicine and Dentistry, Queen Mary University of London, London, UK.
² Practice Dr. Lammel, Ramsau am Dachstein, Austria.
³ Institute of General Practice and Evidence-based Health Services Research, Medical University of Graz, Graz, Austria.
⁴ Institute of General Practice, Goethe-University Frankfurt am Main, Frankfurt am Main, Germany.
⁵ Center for Virology, Medical University of Vienna, Vienna, Austria.
⁶ Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department for Medicine, University of Oxford, Oxford, UK.
⁷ The Queen's College, University of Oxford, Oxford, UK.
⁸ Institute for Global Health, University College London, London, UK.
⁹ Institute for Advanced Studies, Vienna, Austria.
¹⁰ London School of Economics and Political Science, London, UK.

Abstract

Background: Testing for COVID-19 with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) may result in delayed detection of disease. Antigen detection via lateral flow testing (LFT) is faster and amenable to population-wide testing strategies. Our study assesses the diagnostic accuracy of LFT compared to RT-PCR on the same primarycare patients in Austria.

Methods: Patients with mild to moderate flu-like symptoms attending a general practice network in an Austrian district (October 22 to November 30, 2020) received clinical assessment including LFT. All suspected COVID-19 cases obtained additional RT-PCR and were divided into two groups: Group 1 (true reactive): suspected cases with reactive LFT and positive RT-PCR; and Group 2 (false non-reactive): suspected cases with a non-reactive LFT but positive RT-PCR.

Findings: Of the 2,562 symptomatic patients, 1,037 were suspected of COVID-19 and 826 (79.7%) patients tested RT-PCR positive. Among patients with positive RT-PCR, 788/826 tested LFT reactive (Group 1) and 38 (4.6%) non-reactive (Group 2). Overall sensitivity was 95.4% (95%CI: [94%,96.8%]), specificity 89.1% (95%CI: [86.3%, 91.9%]), positive predictive value 97.3% (95%CI:[95.9%, 98.7%]) and negative predictive value 82.5% (95%CI:[79.8%, 85.2%]). Reactive LFT and positive RT-PCR were positively correlated (r = 0.968,95CI=[0.952,0.985] and $κ = 0.823$ , 95%CI=[0.773,0.866]). Reactive LFT was negatively correlated with Ct-value ( r = -0.2999, p < 0.001) and pre-test symptom duration (r = -0.1299,p = 0.0043) while Ct-value was positively correlated with pre-test symptom duration (r = 0.3733),p < 0.001).

Interpretation: We show that LFT is an accurate alternative to RT-PCR testing in primary care. We note the importance of administering LFT properly, here combined with clinical assessment in symptomatic patients.

Funding: Thomas Czypionka received funding from the European Union's Horizon 2020 Research and Innovation Programe under the grant agreement No 101016233 (PERISCOPE). No further funding was available for this study.

Keywords: COVID-19, Primary care; Lateral flow antigen testing; Point-of-care testing; SARS-CoV-2; Sensitivity; Specificity.