Comparison of the Diagnostic Performance of a Rapid Antigen Test with Real-Time Polymerase Chain Reaction for Detection of SARS-CoV-2 Among Patients Diagnosed with COVID-19 at Selected Hospitals in Addis Ababa, Ethiopia

Abstract

Background When faced with a public health problem such as the COVID-19 pandemic, devising a test with an accurate and rapid diagnostic capacity is critical to contain the disease. We compared the diagnostic performance of a rapid antigen test in comparison with a reference method, namely a real-time polymerase chain reaction (RT-PCR) assay. Methods We enrolled patients with confirmed COVID-19 from two selected hospital in Addis Ababa, Ethiopia, between January and November 2021. We assessed the performance of the Standard Q COVID-19 Ag Kit (SD Biosensor, Republic of Korea) in 200 nasopharyngeal and nasal swab samples. Results Out of the 200 samples utilized for the diagnostic performance evaluation, equal proportion of the samples were confirmed positive and negative for SARS-CoV-2 based on RT-PCR. Of the 100 confirmed positive cases, 95 showed positive results with the rapid antigen test, yielding a sensitivity of 95% (95% confidence interval [CI] 88.7–98.4%). Of the 100 confirmed negative cases, there were three false-positive results, yielding a specificity of 97% (95% CI 91.5–99.4%). The sensitivity of the rapid antigen test was higher for samples with an RT-PCR cycle threshold (Ct) value ≤25 compared with samples with a higher Ct value. Conclusion The finding demonstrated that the detection capacity of the Standard Q COVID-19 Ag Test meets the requirements set by the Ministry of Health Ethiopia. The high sensitivity and specificity of the test device indicate the possibility of using it for diagnostic and clinical purposes in resource-constrained settings such as Ethiopia.

The diagnostic performance evaluation of Panbio and STANDARD Q coronavirus disease 2019 antigen tests against real-time polymerase chain reaction in southern Ethiopia

“…The performance demonstrated in our study was in line with the previous studies 10 , 11 . However, our findings indicated lower sensitivities compared to reports from Thailand (98.3%) 7 and Korea (94.9%) 12 for the STANDARD Q; and from Ethiopia (95%) for Panbio 13 . Possible explanations for the relatively lower sensitivities in our study might be associated with the lower viral loads in our study participants.…”

“…This finding was in agreement with results reported in the Netherlands 16 , Korea 12 , and Spain 18 . Similar results have been found by other research in samples with low CT values due to high virus loads 11 , 13 , 19 , 20 . This might suggest that an elevated viral load, which is connected to viral infectivity, is indicated by a positive antigen test 21 .…”