Q-Plex™ Product Overview

SARS-CoV-2 Human IgG (4-Plex)

SARS-CoV-2 Human IgG (4-Plex)

Principle of the Assay

Quansys Biosciences’ SARS-CoV-2 Human IgG (4-Plex) Q-Plex multiplex assay is a qualitative enzyme-linked immunosorbent assay that detects IgG antibodies to SARS-CoV-2 in human serum or plasma. SARS-CoV-2 is the novel coronavirus that causes COVID-19. The SARS-CoV-2 virus has several structural proteins including two spike proteins, S1 and S2. When an individual is infected with the SARS-CoV-2 virus, their immune system produces antibodies to these viral proteins. The typical immune response produces detectable antibody levels ~8-10 days following the onset of symptoms.

The SARS-CoV-2 Human IgG (4-Plex) Q-Plex Multiplex ELISA detects IgG antibodies to both the S1 and S2 spike proteins present in a blood sample. If antibodies are detected, the result will be considered positive. If antibodies are not detected, the result will be considered negative. The assay only detects IgG antibodies, not other classes of antibodies such as IgM or IgA.

The multiplex assay allows for simultaneous indirect ELISA on the following four printed spots:

1- SARS-CoV-2 Spike Glycoprotein (S1), a recombinant antigen which contains amino acids 1-674 of subunit 1. Spike S1 is expressed in mammalian HEK293 cells with a Sheep Fc-Tag.

2- SARS-CoV-2 Spike Glycoprotein (S2) is a recombinant antigen which contains the Spike subunit 2 protein, amino acids 685-1211. Spike S2 is expressed in mammalian HEK293 cells with a Sheep Fc-Tag.

3- Sheep Fc, is a negative control to ensure no cross-reactivity occurs between human IgGs in the sample and the Fc-Tag on the SARS-Cov-2 Spike proteins.

4- Anti-Human IgG is a positive control to ensure the kit performs and the IFU was followed correctly.

SARS-CoV-2 Human IgG (4-Plex) details

Species: Human
Assay Type: Indirect
Sample Type: Human Serum, Plasma
Assay Length: 2 hours
Specificity: See Assay Validation Below
Volume Required Per Well: Min 2µl
Detection Method: Chemiluminescent
Multiplex Format: 96-well solid plate
Catalog No: 691649HU


The Q-Plex™ SARS-CoV-2 Human IgG (4-plex) is a qualitative chemiluminescent assay (ELISA) allowing concurrent measurement of human IgG antibodies to SARS-CoV-2 S1 and SARS-CoV-2 S2 proteins in serum and plasma samples.


Sensitive, reproducible, and convenient 96-well format requiring low sample volumes


Requires the Q-View™ Imaging System for analysis

Assay Validation

The Quansys SARS-CoV-2 Human IgG (4-Plex) ELISA tests for IgG antibodies to either the SARS-CoV-2 S1 protein or the SARS-CoV-2 S2 protein. Our validation studies identified measurable improvement in clinical performance when results from the S1 and S2 assays are considered together rather than single assays (see assay validation data below). Quansys recommends that a sample should only be considered positive for the presence of SARS-CoV-2 reactive IgGs when antibodies reactive to both S1 and S2 are detected.

Negative samples, collected prior to August 2019, and known positive samples collected from individuals who tested positive for COVID-19 on a molecular test at least 14 days prior to sample collection were used to determine clinical sensitivity and specificity.

Evaluating the S1 and S2 simultaneously allows for greater clinical sensitivity and specificity.

The combined S1 & S2 reactive antibody assay demonstrates:
Estimated Sensitivity (PPA) 97%
Estimated Specificity (NPA) 100%
PPV 100%
NPV 100%</td?
SARS-CoV-2 IgG Assay Characteristics
Principle Indirect ELISA
Sample Type Serum, Plasma, Whole Blood
Sample Volume 2 µL
Assay Incubation 2 hours, RT
Total Wash Steps 3
Within Plate Reproducibility 8% CV
Between Plate Reproducibility 10% CV

Assay Kit Information


Each kit contains a 96-well plate, featuring the relevant biomarker panel in each well, and all reagents required to perform testing.

Reagents Include:

  • Detection Mix
  • Controls
  • Substrate
  • Sample Diluents
  • Streptavidin HRP
  • Wash Buffer

All Quansys Q-Plex™ Multiplex and Singleplex assays require the use of the Q-View™ software to read and interpret the test results. A fully-functional, free trial version of the software is available to download, install, and use to analyze your first kit(s). At the end of the trial period, a purchased license is required to continue the use of the Q-View software.

Q-Plex arrays are developed and optimized to work with Q-View imagers. Quansys does not guarantee the results obtained from other imagers and not all imagers are compatible with Quansys Q-Plex arrays.

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