Sample collection and procedure of the INDICAID COVID-19 Rapid Antigen Test

To conduct an INDICAID Rapid Test, a nasal swab sample is collected by inserting the provided swab 1 inch into the nasal cavity. The swab is rubbed against the inside walls of both nostrils 5 times in a large circular path. The swab is then dipped into a buffer solution to elute the sample. Finally, three drops of the buffer solution-specimen mix are applied to the LFA test device. After 20 minutes, the user observes the test device for the presence or absence of a test line that indicates detection of the SARS-CoV-2 antigen. An Internal Quality Control line is included to indicate whether the test has been performed correctly.

Populations and study locations

Between November 30, 2020 and January 8, 2021, study participants were enrolled at two US clinical sites, CityHealth Urgent Care San Francisco, CA and CityHealth Urgent Care Oakland, CA.

As part of the inclusion criteria, study participants were required to be at least 5 years of age and report onset of at least two of the following COVID-19 symptoms within 5 days or less: fever or chills, fatigue, sore throat, congestion or runny nose, cough, headache, diarrhea, shortness of breath or difficulty breathing, muscle or body aches, new loss of taste or smell, nausea, or vomiting. A patient enrichment strategy was implemented to increase the rate of SARS-CoV-2 positive participants enrolled at the CityHealth Urgent Care Oakland, CA site. For this strategy, patients presenting at the clinic were first tested by CityHealth Urgent Care staff, as part of the standard-of-care, with an FDA EUA rapid antigen test (Quidel Sofia SARS Antigen FIA) to pre-screen potential subjects prior to study enrollment. CityHealth Urgent Care staff were asked to identify patients with preliminary positive or negative results for study screening. The trained study operators, blinded to the original patient standard-of-care result, performed specimen collection, processing, and testing. An equal number of positives and negatives were pre-screened by the CityHealth Urgent Care staff at the CityHealth Urgent Care Oakland, CA site. Five unique study operators with varying healthcare backgrounds (licensed medical assistants and registered nurses) conducted the study between the two sites.

Between February 6, 2021 and March 9, 2021, study participants were enrolled at a third US clinical testing site (San Fernando Recreation Park in San Fernando, CA) who were at least 5 years of age and reported at least one of the COVID-19 symptoms listed above. Five unique study operators with varying healthcare backgrounds (licensed medical assistants and registered nurses) conducted the study at the San Fernando, CA site.

Testing procedure

Following the standard of care, patients were asked to provide a total of three nasal swab samples: a self-collected and observed nasal swab sample, followed by a second and third nasal swab sample that were collected by the health care provider (HCP). For the self-collected sample, the HCP provided specimen collection instructions and observed the specimen collection by the patient. The order of the second and third HCP-collected samples was randomized for testing with the investigational antigen test and a comparator method to ensure that bias was not introduced due to unequal distribution of viral material. Immediately after sample collection, the samples for the RT-PCR reference method were stored in viral transport media, while the other two nasal swabs were tested directly with the INDICAID Rapid Test according to the instructions for use (IFU).

INDICAID Rapid Test samples were tested immediately on-site after collection with no storage in accordance with the manufacturer’s protocol. Results of the INDICAID Rapid Test were interpreted by the test operators and recorded as “Positive,” “Negative”, or “Invalid” based on the visual presence or absence of the control and test lines on the developed test strip. Test results were recorded after 20 minutes of assay development by one individual operator per participant.

At the Oakland, CA and San Francisco, CA study sites, swab samples collected for RT-PCR were transferred to DNA/RNA Shield (Zymo Research, Irvine, CA), stored at room temperature, and shipped overnight at ambient temperature to Curative, Inc. (San Dimas, CA) per the manufacturer’s protocol for laboratory testing. The Curative SARS-CoV-2 Assay, an FDA Emergency Use Approved (EUA) test, was used as the RT-PCR reference method [10].

At the San Fernando, CA study site, swab samples collected for RT-PCR were transferred to BioCollections VTM (BioCollections Worldwide, Inc., Miami, FL), stored on ice packs, and shipped overnight on ice packs to BioCollections Worldwide, Inc. per the manufacturer’s protocol for laboratory testing. BioCollections first performed the FDA EUA assay Hologic Aptima SARS-CoV-2 to determine the SARS-CoV-2 status of each patient sample. The remaining volume from positive specimens were then stored frozen at -70°C and later analyzed with the FDA EUA BioCollections Worldwide SARS-CoV-2 Assay to obtain cycle threshold (Ct) results.