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

Abstract

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.

Evaluation of the Access Bio CareStart™ rapid SARS-CoV-2 antigen test in asymptomatic individuals tested at a community mass-testing program in Western Massachusetts

“…Compared to a RT-qPCR-based test, we found a much lower sensitivity (49.0%) than what was reported in the FDA package insert (87.2%), which was restricted to 39 symptomatic individuals within 5 days of symptom onset (24). However, this sensitivity was consistent with the reported sensitivity of CareStart in asymptomatic individuals recruited in a recent study at Lawrence General Hospital in Massachusetts (84.8%) (17). Compared to the Abbott BinaxNOW RDT, which has been validated in several studies including a recent study in Massachusetts, the sensitivity of the CareStart RDT was lower overall and when using a Ct positivity cutoff of ≤ 30 (15).…”

“…The copyright holder for this preprint this version posted June 20, 2021. ; https://doi.org/10.1101/2021.06.17.21259109 doi: medRxiv preprint clear impact on the sensitivity of the CareStart RDT, where concordant results showed lower Ct values. In contrast, discordant results had higher Ct values, a proxy for lower viral load, as reported in other evaluations (15,17,32). Consistent with this, the CareStart RDT sensitivity improved with a RT-qPCR positivity Ct cut-off of < 30.…”

“…The test provides two cycle threshold (Ct) values, one for the nucleocapsid (N2) gene, and one for an internal positive control RNaseP gene. We compared the sensitivity of CareStart against both the qualitative binary RT-qPCR results and the Ct values of the N2 gene amplification reaction, as previously described (17). We calculated sensitivity, specificity, PPV and NPV of the RDT from 2 x contingency tables using RT-qPCR as the gold standard reference.…”

“…The copyright holder for this preprint this version posted June 20, 2021. ; https://doi.org/10.1101/2021.06.17.21259109 doi: medRxiv preprint Suliman et al Performance of CareStart™ SARS-CoV-2 rapid antigen test in detecting SARS-CoV-2 infection in asymptomatic carriers. In fact, several independent evaluations demonstrate the decreased sensitivity of antigen-detecting RDTs in asymptomatic RT-qPCR positive individuals compared to those with symptoms (14)(15)(16)(17). In the United States, studies thus far have focused on 3 RDTs: Quidel Sofia™ (8,18), BD Veritor™ (13,19) and Abbott BinaxNOW™ (15,16,20).…”

“…In this study, we evaluated the Access Bio CareStart™ COVID-19 RDT (CareStart), a chromatographic antigen-detecting lateral flow immunoassay that received EUA by the FDA (12,17). We evaluated CareStart in asymptomatic and mildly symptomatic individuals presenting for routine testing at one of the 'Stop the Spread' free community testing sites in Holyoke, Massachusetts.…”