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Performance study of the anterior nasal AMP SARS-CoV-2 rapid antigen test in comparison with nasopharyngeal rRT-PCR

Introduction. The gold standard for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection is real-time reverse transcription PCR (rRT-PCR), which is expensive, has a long turnaround time and requires special equipment and trained personnel. Nasopharyngeal swabs are uncomfortable, not suitable for certain patient groups and do not allow self-testing. Convenient, well-tolerated rapid antigen tests (RATs) for SARS-CoV-2 detection are called for. Gap statement. More real-life performance data on anterior nasal RATs are required. Aim. We set out to evaluate the anterior nasal AMP RAT in comparison with rRT-PCR in a hospital cohort. Methodology. The study included 175 patients, either hospitalized in a coronavirus disease 2019 (COVID-19) ward or screened in a preadmittance outpatient clinic. Two swabs were collected per patient: an anterior nasal one for the RAT and a combined naso-/oropharyngeal one for the rRT-PCR. Sixty-five patients (37%) were rRT-PCR-positive [cycle threshold (C t) <40]. Results. The anterior nasal AMP RAT showed an overall sensitivity and specificity of 29.2 % (18.6–41.8, 95 % CI) and 100.0 % (96.7–100.0, 95 % CI) respectively. In patients with a C t value <25, <30 and <33, higher sensitivities were observed. Time since symptom onset was significantly higher in patients with a false-negative RAT (P=0.02). Conclusion. The anterior nasal AMP RAT showed low sensitivities in this cohort, especially in patients with a longer time since symptom onset. Further knowledge concerning the viral load and antigen expression over time and in different swabbing locations is needed to outline the usage time frame for SARS-CoV-2 RAT.