Evaluation of commercially available immuno-magnetic agglutination and enzyme-linked immunosorbent assays for rapid point-of-care diagnostics of COVID-19

Introduction: Coronavirus Disease 2019 (COVID-19) is caused by severe acute respiratory coronavirus-2 (SARS-CoV-2). Fast, accurate and simple blood-based assays for quantification of anti-SARS-CoV-2 antibodies are urgently needed to identify infected individuals and keep track of the spread of disease. Methods: The study included 35 plasma samples from 22 individuals with confirmed COVID-19 by real time reverse transcriptase polymerase chain reaction and 40 non COVID-19 plasma samples. Anti-SARS-CoV-2 IgM/IgA or IgG antibodies were detected by a microfluidic quantitative immunomagnetic assay (IMA)(ViroTrack Sero COVID IgM+IgA/IgG Ab, Blusense Diagnostics, Denmark) and by enzyme-linked immunosorbent assay ((ELISA) (EuroImmun Medizinische Labordiagnostika, Germany). Results: Of the 35 plasma samples from the COVID-19 patients, 29 (82.9%) were positive for IgA/IgM or IgG by IMA and 29 samples (82.9%) were positive by ELISA. Sensitivity for only one sample per patient was 68% for IgA+IgM and 73% IgG by IMA and 73% by ELISA. For samples collected 14 days after symptom onset, the sensitivity of both IMA and ELISA was around 90%. Specificity of the IMA reached 100% compared to 95% for ELISA IgA and 97.5% for ELISA IgG. Conclusion: IMA for COVID-19 is a rapid simple-to-use point of care test with sensitivity and specificity similar to a commercial ELISA.

A potentiometric magnetic immunoassay for rapid detection of Salmonella typhimurium

We propose an immunomagnetic assay coupled to potentiometric detection suitable for sensitive (limit-of-detection 20 cells per mL) and rapid (assay time of 75 minutes) detection ofSalmonella typhimurium.