Abstract
BackgroundTesting 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.MethodsPatients 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.FindingsOf 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 , 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).InterpretationWe 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.FundingThomas 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.
Highlights
Non-pharmaceutical interventions (NPIs) that include imposing severe social distancing restrictions on a nationalResearch in contextEvidence before this studyAn effective test strategy is crucial for the detection of SARS-CoV-2 and lateral flow testing (LFT) may be a quick alternative to quantitative reverse transcriptase-polymerase chain reaction (RT-PCR)
We provide evidence that LFT can accurately detect SARS-CoV-2 infection as an alternative to RT-PCR testing among symptomatic patients in a real-life primary care setting across a large geographical area
Between October 22 and November 30, 2020, 2562 patients with mild to moderate flu-like illness were clinically assessed and tested with LFT across the 20 intervention practices (Fig. 1). 1525 patients, who tested LFT non-reactive and who presented with signs and symptoms suggesting a different type of infection, were not suspected of having COVID-19 and excluded from this analysis
Summary
An effective test strategy is crucial for the detection of SARS-CoV-2 and lateral flow testing (LFT) may be a quick alternative to quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Evidence for effective symptomatic case detection with LFT at scale, in primary care and on the same patient cohort tested with PT-PCR is limited. We provide evidence that LFT can accurately detect SARS-CoV-2 infection as an alternative to RT-PCR testing among symptomatic patients in a real-life primary care setting across a large geographical area. Noting that in our study LFT was administered by self-taught clinicians and delivered at scale in primary care, we allude to the important aspect that population-wide LFT testing requires accurate administration of the test and this needs to be part of the planning strategy.
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