A Microflow Cytometry-based Agglutination Immunoassay for On-site Antigen or Antibody-based Medical Diagnosis

Abstract

On-site medical diagnosis is of great importance as it can provide cost-effective, user-friendly, and time-saving diagnosis, especially for individuals who live in resource-limited environments. The microflow cytometry-based agglutination immunoassay (MCAIA) for on-site antigen or antibody-based medical diagnosis was proposed. A method that is based on the average transit time of assay mixtures for quantitative detection of antigens of antibodies was proposed and verified by experimental results. C-reactive protein (CRP) detection was used to illustrate the principle of antigen detection by the MCAIA. A linear relationship between the proportion of monomers and the concentration of CRP was established when data was analyzed using amplitude. A linear relationship between the average transit time and the concentration of CRP was established. A limit of detection (LOD) of 0.09 mg/L and an assay range up to 1 mg/L were achieved when data was analyzed using transit time. The total assay time was approximately 10 min and only a 10 µL sample was needed for each detection. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody detection was chosen as a model to demonstrate the principle of antibody detection by the MCAIA. A relationship between the average transit time and the concentration of SARS-CoV-2 immunoglobulin M (IgM) was established. A LOD of 0.06 mg/L and an assay range up to 1 mg/L were achieved. A relationship between the average transit time and the concentration of SARS-CoV-2 immunoglobulin G (IgG) was established. A LOD of 0.1 mg/L and an assay range up to 1 mg/L was achieved. The assay time of the SARS-CoV-2 antibody detection was approximately 30 min and only a 10 µL sample was needed for each test. The proposed MCAIA can be broadly applied to other kinds of antigens or antibodies for on-site detection by replacing the corresponding antibodies or secondary antibodies specific to the targeted analyte. The compacted setup is competitive with other technologies for the medical diagnosis of antigens and antibodies.