ABSTRACT
BackgroundTo 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. MethodsConsenting 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. ResultsOf 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. ConclusionsCareStart 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.
ABSTRACT
BackgroundRapid diagnostic tests (RDTs) for SARS-CoV-2 antigens (Ag) that can be performed at point-of-care (POC) can supplement molecular testing and help mitigate the COVID-19 pandemic. Deployment of an Ag RDT requires an understanding of its operational and performance characteristics under real-world conditions and in relevant subpopulations. We evaluated the Abbott BinaxNOW COVID-19 Ag Card in a high-throughput, drive-through, free community testing site in Massachusetts (MA) using anterior nasal (AN) swab RT-PCR for clinical testing. MethodsIndividuals presenting for molecular testing in two of seven lanes were offered the opportunity to also receive BinaxNOW testing. Dual AN swabs were collected from symptomatic and asymptomatic children ([≤] 18 years) and adults. BinaxNOW testing was performed in a testing pod with temperature/humidity monitoring. One individual performed testing and official result reporting for each test, but most tests had a second independent reading to assess inter-operator agreement. Positive BinaxNOW results were scored as faint, medium, or strong. Positive BinaxNOW results were reported to patients by phone and they were instructed to isolate pending RT-PCR results. The paired RT-PCR result was the reference for sensitivity and specificity calculations. ResultsOf 2482 participants, 1380 adults and 928 children had paired RT-PCR/BinaxNOW results and complete symptom data. 974/1380 (71%) adults and 829/928 (89%) children were asymptomatic. BinaxNOW had 96.5% (95% confidence interval [CI] 90.0-99.3) sensitivity and 100% (98.6-100.0) specificity in adults within 7 days of symptoms, and 84.6% (65.1-95.6) sensitivity and 100% (94.5-100.0) specificity in children within 7 days of symptoms. Sensitivity and specificity in asymptomatic adults were 70.2% (56.6-81.6) and 99.6% (98.9-99.9), respectively, and in asymptomatic children were 65.4% (55.6-74.4) and 99.0% (98.0-99.6), respectively. By cycle threshold (Ct) value cutoff, sensitivity in all subgroups combined (n=292 RT-PCR-positive individuals) was 99.3% with Ct [≤]25, 95.8% with [≤]30, and 81.2% with [≤]35. Twelve false positive BinaxNOW results (out of 2308 tests) were observed; in all twelve, the test bands were faint but otherwise normal, and were noted by both readers. One invalid BinaxNOW result was identified. Inter-operator agreement (positive versus negative BinaxNOW result) was 100% (n = 2230/2230 double reads). Each operator was able to process 20 RDTs per hour. In a separate set of 30 specimens (from individuals with symptoms [≤]7 days) run at temperatures below the manufacturers recommended range (46-58.5{degrees}F), sensitivity was 66.7% and specificity 95.2%. ConclusionsBinaxNOW had very high specificity in both adults and children and very high sensitivity in newly symptomatic adults. Overall, 95.8% sensitivity was observed with Ct [≤] 30. These data support public health recommendations for use of the BinaxNOW test in adults with symptoms for [≤]7 days without RT-PCR confirmation. Excellent inter-operator agreement indicates that an individual can perform and read the BinaxNOW test alone. A skilled laboratorian can perform and read 20 tests per hour. Careful attention to temperature is critical.
