A Field Evaluation of the Covid-19 Antigen Testing Regimen at a Primary Hospital in Ghana

Abstract

Background: Accurate, reliable and rapid diagnostic tools for COVID-19 are essential for tackling the ongoing pandemic, especially in the developing world. This study aimed to assess the performance and viability of the testing regimen at a district-level hospital testing centre where both nasopharyngeal and oropharyngeal samples are taken simultaneously but the samples are tested separately. The nasopharyngeal samples are tested using the SD Biosensor Standard F Covid-19 FIA antigen test kit whiles RT-PCR is conducted on the oropharyngeal samples. Methods: A retrospective analysis was conducted on 314 paired samples taken from March to August 2021 whereby the dual testing scheme was applied. The field diagnostic performance of the Standard F Antigen test was compared with Reverse Transcription Polymerase Chain Reaction (RT-PCR) results. The sensitivity, specificity and expected predictive values were then evaluated. The RT-PCR is the gold standard for Covid-19 testing. Results: A total of 314 matched Covid-19 Antigen Rapid Diagnostic Test (Ag-RDT) and RT-PCR samples were analysed retrospectively. The sensitivity and specificity of the Ag-RDT was 80.85% (95% Confidence interval of 66.74% – 90.85%) and 98.9% (95% Confidence interval of 96.74% – 99.77%) respectively. The overall accuracy was determined to be 96.2% with a Cohen’s Kappa score of 0.84 indicating an almost perfect agreement. Conclusion: The results of samples taken from the different anatomical sites have an almost perfect agreement. Therefore, the performance of the Standard F Covid-19 antigen test kit is optimal and the testing regimen at the hospital is adequate. It can thus be replicated at other testing sites. However, adequate training in the sampling procedure, storage, transport as well as stringent monitoring and supervision is required.