Performance and Operational Evaluation of the Access Bio CareStart Rapid Antigen Test in a High-throughput Drive-through Community Testing Site in Massachusetts

Pollock, Nira R; Tran, Kristine; Jacobs, Jesica R; Cranston, Amber E; Smith, Sita; O’Kane, Claire Y; Roady, Tyler J; Moran, Anne; Scarry, Alison; Carroll, Melissa; Volinsky, Leila; Perez, Gloria; Patel, Pinal; Gabriel, Stacey; Lennon, Niall J; Madoff, Lawrence C; Brown, Catherine; Smole, Sandra C

BACKGROUND: To facilitate deployment of point-of-care testing for SARS-CoV-2, we evaluated the Access Bio CareStart COVID-19 Antigen test in a high-throughput, drive-through, free community testing site using anterior nasal (AN) swab RT-PCR for clinical testing. METHODS: Consenting symptomatic and asymptomatic children (≤18 years) and adults received dual AN swabs. CareStart testing was performed with temperature/humidity monitoring. All tests had two independent reads to assess inter-operator agreement. Patients with positive CareStart results were called and instructed to isolate pending RT-PCR results. The paired RT-PCR result was the reference for sensitivity and specificity calculations. RESULTS: Of 1603 participants, 1245 adults and 253 children had paired RT-PCR/CareStart results and complete symptom data. 83% of adults and 87% of children were asymptomatic. CareStart sensitivity/specificity were 84.8% (95% confidence interval [CI] 71.1-93.7)/97.2% (92.0-99.4) and 85.7% (42.1-99.6)/89.5% (66.9-98.7) in adults and children, respectively, within 5 days of symptoms. Sensitivity/specificity were 50.0% (41.0-59.0)/99.1% (98.3-99.6) in asymptomatic adults and 51.4% (34.4-68.1)/97.8% (94.5-99.4) in asymptomatic children. Sensitivity in all 234 RT-PCR-positive people was 96.3% with cycle threshold (Ct) ≤25, 79.6% with Ct ≤30, and 61.4% with Ct ≤35. All 21 false positive CareStart tests had faint but normal bands. Inter-operator agreement was 99.5%. Operational challenges included identification of faint test bands and inconsistent swab elution volumes. CONCLUSIONS: CareStart had high sensitivity in people with Ct ≤25 and moderate sensitivity in symptomatic people overall. Specificity was unexpectedly lower in symptomatic versus asymptomatic people. Excellent inter-operator agreement was observed, but operational challenges indicate that operator training is warranted.