A novel SARS-CoV-2 IgG line-blot for evaluating discrepant IgG test results – Observations in pre-pandemic and follow-up samples of five patients

To confirm discrepant SARS-CoV-2-IgG results in four standard assays we applied for the first time a prototype of a coronavirus IgG-line-blot which employs antigens from seasonal coronaviruses, SARS-1 and SARS-CoV-2 combined with avidity testing as a confirmatory tool in a follow-up of five cases including pre-pandemic samples.