CareStart™ COVID-19 Antigen Test Performance Characteristics
To initially evaluate the clinical performance of the CareStart™ COVID-19 Antigen test, a total of 126 blinded frozen swab samples, including 106 retrospective clinical specimens and 20 contrived specimens, were tested in one (1) CLIA waived investigational site by five (5) minimally trained operators in the U.S during the 2020 COVID-19 season.
A total of 126 frozen samples consisting of 43 positive nasopharyngeal (NP) swabs, 63 negative NP swab specimens, and 20 contrived near the cut-off samples (10 positives and 10 negatives). NP swab specimens collected from the patients with COVID-19 like symptoms in the U.S during the 2020 COVID-19 season and stored in BD universal transport media tube were provided by multiple vendors in the U.S. All the NP swab specimens were confirmed as positive or negative and validated with Ct value by the FDA EUA RT-PCR as a comparator method prior to the study. The specimens were aliquoted, randomized, and blinded into sample panels that was tested by each operator, using the instructions provided by the Quick Reference Instructions (QRI).
In addition to the clinical population, a total of 20 contrived near the cut-off samples, 10 low positives near the Limit of Detection (LoD) (2x LoD), and 10 negatives (zero analytes) samples, were prepared using the inactivated SARS-CoV-2 strain spiked into the simulated nasal swab matrix, BD universal transport media. The heat-inactivated SARS-CoV-2 isolate USA-WA1/2020 was used to prepare the positive samples. The contrived near the cut-off samples were added to the clinical population and tested at the same study site by the same operators. All the study samples were randomized and assigned with unique study subject ID by the sponsor prior to testing at the study site. The expected results of the samples were completely blinded to the operators. All the samples were tested by five (5) operators according to the Quick Reference Instructions only.
A total of 126 frozen swab samples were considered evaluable in this study. The performance of the CareStart™ COVID-19 Antigen as compared to the RT-PCR comparator method are presented in the table below:
The clinical performance characteristics of CareStart™ COVID-19 Antigen test is currently being evaluated in a multi-site prospective study in the U.S in which NP swabs from patients are sequentially enrolled and tested. A total of five (5) investigational sites throughout the U.S are participating in the study. Testing is performed by operators with no laboratory experience and who are representative of the intended users. Operators are only using the QRI for the test without any training provided. The patients presenting the COVID-19 like symptoms within five (5) days of symptom onset at the study sites are enrolled. An FDA EUA RT-PCR assay for the detection of SARS-CoV-2 from a NP or nasal swab is utilized as the comparator method for the study. The initial six (6) positive patient results are presented as below.
Analytical Sensitivity: Limit of Detection (LoD)
The LoD for direct swab was established using heat-inactivated SARS-CoV-2 isolate USAWA1/2020 (NR-52286). The strain was spiked into the pooled human nasal swab matrix obtained from multiple healthy volunteers eluted in VTM and confirmed as SARS-CoV-2 negative by RT-PCR to prepare positive samples. The estimated LoD found from the initial twofold serial dilution test was confirmed by testing 20 replicates. The confirmed LoD for direct swab was 8 x 102 TCID50/ml.
The LoD for swab in VTM (BD universal transport media) was established using heat-inactivated SARS-CoV-2 isolate USA-WA1/2020 (NR-52286). The two-fold serial diluted strain stocks were spiked into each of 3 ml human nasal swab matrix obtained from multiple healthy volunteers eluted in 3 ml VTM tube. The estimated LoD found from the initial two-fold serial dilution test was confirmed by testing 20 replicates. The confirmed LoD for swab in VTM was 6.4 x 103 TCID50/ml.