Introduction

In order to be able to measure antibodies in patient plasma/serums in high throughput, the xMAP® technology from Luminex® is used. In the process, proteins of e.g. pathogenic microorganisms are covalently bound to magnetic particles only a few micrometers in size (MagPlex™). A unique fluorescence signature for each particle species makes it possible to re-identify the individual magnetic spheres in mixtures. Thus, different bacterial antigens can be analyzed in a multiplex approach.

The immune response to some antigens can be extremely strong and extremely weak to others. Thus, the quantitative dynamic range of analysis extends over several orders of magnitude. In a standard measurement, the patient’s plasma/serum is diluted 1000-fold and / or e.g. 10000-fold. Since this commonly used approach carries the risk of generating quantitative data at saturation or detection limits, a novel approach has been developed that measures patient series in a serial dilution series with 7 dilution levels (e.g., 50-fold to 200,000-fold) (Figure 1).

serological assay workflow using the xMAP® technology

insepct serological assay workflow using the xMAP® technology

The resulting variable data could not be analyzed with any conventional software. For this an iterative complex analysis procedure was developed and implemented using the programming language R and shiny resulting the the xMAPr app.

xMAPr

xMAPr was developed to analyze and visualize data from bead-based experiments performed with the xMAP® technology. The whole basis of the the analysis is the utilization of serial dilutions per sample to avoid saturation effects. Figure 2 illustrate the mode of operation of xMAPr.