Comparing lateral flow testing with a rapid RT-PCR method for SARS-CoV-2 detection in the United Kingdom-A retrospective diagnostic accuracy study.

Background and Aims: In late 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, China. Rapid global spread led to the coronavirus disease 2019 (Covid-19) pandemic. Accurate detection of SARS-CoV-2 has become a vitally important tool in controlling the spread of the virus. Lateral flow devices (LFDs) offer the potential advantage of speed and on-site testing. The sensitivity of these devices compared to reverse transcription-polymerase chain reaction (RT-PCR) has been questioned. Methods: We compared the sensitivity of the Innova LFD, used widely in the United Kingdom, with our rapid RT-PCR method using stored positive samples. Samples with a range of viral loads (original Ct values 18.9-36.5) were tested. Results: The Innova LFD was found to be 6000-10,000 times less sensitive than RT-PCR for SARS-CoV-2 detection. Overall, the LFD detected 46.2% of the positives detected by RT-PCR, with 50% of these observed to be weak LFD positives. At lower viral loads, such as 10,000-100,000 RNA copies/ml, the LFD detected 22.2% of positives. In addition, two strong positives (3 and 1.5 million RNA copies/ml) were not detected by the LFD. Conclusion: The argument for use of LFD kits is that they detect infectious virus and hence contagious individuals. However, there is a lack of conclusive evidence supporting this claim. The Innova LFD has been subject to a Class I recall by the US Food and Drug Administration, but is still approved and widely used in the United Kingdom.