SARS-CoV-2 IgG Assay Precision and Specificity

A 5-day precision study according to CLSI EP5-A3 guidelines was performed using a panel of 6 plasma samples, prepared by either spiking or diluting as necessary to obtain negative, slightly positive, and moderately positive samples. The panel samples were tested with the LIAISON SARS-CoV-2 S1/S2 IgG assay in 6 replicates per run and 3 runs per day for 5 operating days on one LIAISON XL analyzer (n = 90).
A cross-reactivity study was performed to evaluate other SARS viruses (human CoV-229E [HCoV-229E], HCoV-HKU1, HCoV-OC43, and untyped HCoV), and samples from patients with conditions caused by other viruses, other organisms, or atypical immune system activity (nuclear autoantibodies, herpesvirus B, herpesvirus C, influenza A virus, influenza B virus, respiratory syncytial virus, Borrelia burgdorferi, Mycoplasma pneumoniae, Epstein-Barr virus, cytomegalovirus, herpes simplex viruses 1 and 2, human anti-mouse antibodies, parvovirus B19, rheumatoid factor, rubella virus, and varicella zoster virus). Samples for the evaluation were collected before October 2019, prior to the COVID-19 pandemic. In addition, samples with potentially interfering factors, such as triglycerides, hemoglobin, bilirubin, cholesterol, acetaminophen, ibuprofen, and biotin, were assessed with the LIAISON SARS-CoV-2 S1/S2 IgG assay according to CLSI guidelines.