Ann Clin Virol | Volume 3, Issue 1 | Research Article | Open Access
Shaden S*
Department of Emergency Medicine, Hadassah Mount Scopus, Israel
*Correspondance to: Salameh Shaden
Fulltext PDFBackground: During the COVID-19 pandemic the RT-PCR test was the gold standard. Due its costs, accessibility and time required for RT-PCR testing a demand for rapid point of care tests arose.
Objective: To evaluate the sensitivity and specificity of COVID-19 Ag test and to identify predictive factors for a false negative test in an emergency department setting.
Methods: COVID-19 Ag test was used in the emergency department during the Alpha variant outbreak in Israel. These test results were compared with those obtained by a RT-PCR SARS-CoV-2 assay. Clinical data was collected from all participants.
Results: Sensitivity was 63%, specificity was 100%, positive predictive value was 100% and negative predictive value was 93%. There was a statistically significant difference in the time span from the onset of symptoms and the time of testing between the positive antigen group and negative antigen group, 3.9 days with a SD of 5.6 and 5.6 days with a SD of 4 respectively (OR: 0.93, CI 0.87-0.99, P value 0.025). Statistical difference was noted in patients who presented without gastrointestinal symptoms (51, 32.3% and 107, 67.7% respectively, OR: 0.48, CI 0.25-0.92, P value 0.027). Mean cycle time in subjects with negative antigen test was 29.1 while it was 20.9 in subjects with positive antigen tests (OR: 0.71, CI 0.65-0.78, P<0.001).
Conclusion: This rapid antigen test is highly specific but lacks sensitivity. Positive tests correlate with earlier presentation, absence of gastrointestinal symptoms and lower cycle time which correlates with a higher viral load in the individual. Thus, we do recommend the use of rapid COVID-Ag test up to 2 weeks.
COVID; Rapid Ag test; Cycle Time; Emergency department
Shaden S. COVID-Ag Test Use in the Setting of Emergency Department -Practical Issues. Ann Clin Virol. 2023; 3(1): 1008.