Evaluation of the Panbio rapid antigen test for SARS-CoV-2 in primary health care centers and test sites.

Abstract Background Rapid antigen tests (Ag-RDT) are emerging as new diagnostic tools for COVID-19 and real-world evaluations are needed to establish their performance characteristics. Main objective To evaluate the accuracy of the Panbio Ag-RDT at primary health care (PHC) centers and test sites in symptomatic patients and close contacts, using the Reverse-Transcription Polymerase Chain Reaction (RT-PCR) test as the gold standard. Methods This was a prospective diagnostic study conducted in four PHC centers and two test sites in Mallorca, Spain. Consecutive patients older than 18 years, attending the sites for RT-PCR testing either for suggestive symptoms of infection or a close contact, were included. Two nasopharyngeal samples were collected, one for RT-PCR and the other was processed on-site using the Panbio rapid antigen test kit for SARS-CoV-2. The sensitivity and specificity were calculated using RT-PCR as the reference, and the predictive values using the pretest probability results for each analyzed group. Results A total of 1369 participants were included; mean age 42.5 ± 14.9 years and 54.3% women. The overall prevalence was 10.2%. Most participants (70.6%) presented within 5 days of the onset of symptoms or close contact, and more than 70% had high viral loads. The overall sensitivity was of 71.4% (95% CI: 63.1%, 78.7%), the specificity of 99.8% (95% CI: 99.4%, 99.9%), the positive predictive value of 98.0% (95% CI: 93.0%, 99.7%) and a negative predictive value of 96.8% (95% CI: 95.7%, 97.7%). The sensitivity was higher in symptomatic patients, in those arriving within 5 days since symptom onset and in those with high viral load. Conclusion Ag-RDT had relatively good performance characteristics in suspected symptomatic patients within five days since the onset of symptoms. However, our results concludes that a negative Ag-RDT in these settings must be considered as presumptive. Keywords: COVID-19, rapid antigen test, SAR-COV-2, primary care.