Retrospective Clinical Evaluation of Four Lateral Flow Assays for the Detection of SARS-CoV-2 Antibodies

Coronavirus disease 2019 (COVID-19) is a potentially life-threatening respiratory infection caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), for which numerous serologic assays are available. In a CLIA laboratory setting, we used a retrospective sample set (n = 457) to evaluate two lateral flow immunoassays (LFIAs; two iterations of Rapid Response™ COVID-19 Test Cassette, BTNX Inc.) and a subset of to evaluate SARS-COV-2 IgG/IgM Rapid Test, ACON Laboratories (n = 200); and Standard Q COVID-19 IgM/IgG Duo, SD BIOSENSOR (n = 155) for their capacity to detect of SARS-CoV-2 IgG. In a cohort of primarily hospitalized patients with RT-PCR confirmed COVID-19, the BTNX assays demonstrated 95% and 92% agreement with the Abbott SARS-CoV-2 IgG assay and sensitivity was highest at ≥ 14 days from symptom onset [BTNX kit 1, 95%; BTNX kit 2, 91%]. ACON and SD assays demonstrated 99% and 100% agreement with the Abbott assay at ≥ 14 days from symptom onset. Specificity was measured using 74 specimens collected prior to SARS-CoV-2 circulation in the United States and 31 “cross-reactivity challenge” specimens, including those from patients with a history of seasonal coronavirus infection and was 98% for BTNX kit 1 and ACON and 100% for BTNX kit 2 and SD. Taken with data from EUA assays, these results suggest that LFIAs may provide adequate results for rapid detection of SARS-CoV-2. Replicating these results in fingerstick blood in outpatient populations, would further support the possibility that LFIAs may be useful to increase access to serologic testing