Performance of an Antigen Rapid Test Compared to RT-PCR for the Detection of SARS-CoV-2

Background: Rapid and accurate diagnosis of COVID-19 is critical for the management of patients and to limit the spread of the infection. real-time reverse transcription polymerase chain reaction (RT- PCR) is the gold standard for the diagnosis of SARS-CoV-2 infection, however, it is costly and requires time to obtain a result. A number of alternative rapid tests are available now to provide a faster and more convenient solution for the diagnosis of COVID-19. The aim of this work was to compare the performance of a SARS-Cov-2 Antigen Rapid Test (ART) Cassette to the RT-PCR conventional method.

Methods: Two nasopharyngeal swabs were taken from each of the 126 patients included in this study. Of those, 23 were healthy individuals, 9 were confirmed COVID-19 patients and 103 patients from COVID-19 isolation ward in the hospital. For each patient, one sample was processed for RT-PCR and a second swab was used on the ART kit.

Results: Participants were 57.5% males and 42.5% females. The average age was 54.7 (±14). The QPCR swabs returned 67.9% positivity while the antigen rapid test returned 27.4% positivity. In 56.6% of patients the QPCR results concurred with the rapid test results. Using Fagan nomogram analysis, the 95% confidence interval was (2-20) with a negative likelihood of 0.18. Posterior probability was 0.1. Positive test (blue) prior probability was set at 26%. The 95% confidence interval was (31-41) with a positive likelihood of 1.56. Posterior probability was 0.6.

Conclusion: The ART is a useful and efficient test for diagnosing COVID-19, however, QPCR sensitivity is higher. It is recommended to use ART twice for confirming COVID-19 positivity, which will give a statistically more accurate finding.