Background: Vulnerable cancer patients are at increased risk of severe COVID-19. Early testing and detection is vital to prevent transmission of SARS-CoV-2 to cancer patients and the community. Although rRT-PCR is the gold standard to detect SARS-CoV-2, lateral flow devices (LFDs) for rapid antigen testing are set to become a keystone of SARS-CoV-2 mass community testing because of its convenience and high sensitivity. There is limited information on how well they identify infectious cases. Understanding their performance and limitations is, therefore, essential for successful strategy implementation. A pilot evaluation was performed on two commercial LFDs and assessed their association with PCR cycle threshold (Ct) values.
Methods: Twenty nasopharyngeal swabs tested positive by SARS-CoV-2 rRT-PCR with Ct-value ranged between 18 and 35 were randomly selected for the evaluation with CareStartTM COVID-19 Antigen test and CLINITEST® Rapid COVID-19 Antigen Test in parallel to detect SARS-CoV-2.
Results: In comparison, only one sample with Ct-value of 18 showed positive in both rapid antigen tests. Eighteen samples detected positive with rRT-qPCR were negative with both antigen rapid tests. One invalid result was found on CareStartTM COVID-19 Antigen test kit due to sample quality and insufficient.
Conclusion: Our pilot results suggest that rRT-PCR still be the gold standard for COVID-19 diagnosis. LFDs are suitable for patients with higher viral loads with better antigen detection rates. Among its limitations are the relative low numbers of cases, our pilot study suggested that COVID-19 Ag rapid antigen testing should be used in parallel with rRT-PCR as the routine frontline screening for COVID-19. Further studies are needed to ascertain whether mass screening of SARS-CoV-2 using LFDs has any impact on the transmission of COVID-19 in cancer patients and the community.
Acknowledgement: All samples were kindly provided by KingMed Diagnostics (Hong Kong) Limited.
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Cheung, K., Chu, E., Wu, R., Cheng, C., Kong, A., Ma, O. & Lee, J. 2022, 'P72-5 Is rapid antigen detection test suitable as community screening for SARS-CoV-2?', Annals of Oncology Supplements, 33(SUPPL. 6), pp. S540-. https://doi.org/10.1016/j.annonc.2022.05.343