ABSTRACT
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 29.2â% (18.6-41.8, 95â% CI) and 100.0â% (96.7-100.0, 95â% 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.
ABSTRACT
OBJECTIVES: Quick and inexpensive SARS-CoV-2 screening and frontline testing are in growing demand. Our study aimed to evaluate the performance of the immunochromatographic AMP rapid antigen test (AMP RAT) compared to the gold-standard real-time reverse transcription PCR (rRT-PCR) in a hospital cohort. METHODS: A total of 392 patients, who presented consecutively with COVID-19 symptoms in our emergency department, were included in this retrospective study. Two swabs were collected per patient: a nasopharyngeal for the RAT and a combined naso- and oropharyngeal for the rRT-PCR. A positive rRT-PCR (defined as cycle threshold (Ct) < 40) was found in 94 (24%) patients. RESULTS: In our cohort with a median patient age of 70, overall sensitivity and specificity of the AMP RAT was 69.2% (58.8-78.3, 95% CI) and 99.7% (98.1-100.0, 95% CI), respectively. In patients with a Ct value < 25 and < 30, higher sensitivities of 100.0% (89.4-100.0, 95% CI) and 91.8% (81.9-97.3%, 95% CI) were observed. CONCLUSIONS: The AMP RAT showed a high sensitivity in patients with a Ct value < 25 and < 30 and might be helpful for frontline testing whenever rRT-PCR is not readily available.
