A Novel Utility to Correct for Plate/Batch/Lot and Nonspecific Binding Artifacts in Luminex Data

Cytokines and other secreted soluble proteins are routinely assayed as fluorescence intensities on the Luminex (Luminex, Austin, TX) platform. As with any immunoassay, a portion of the measured Ab binding can be nonspecific. Use of spiked-in microbead controls (e.g., AssayChex Process, Control Panel; Radix Biosolutions, Georgetown, TX) can determine the level of nonspecific binding on a per specimen basis. A statistical approach for correction of this assay's nonspecific binding artifact was first described in earlier work. The current paper describes a novel utility written in the R language (https://www.r-project.org), that refines correction for nonspecific binding in three important ways: 1) via local polynomial regression, the utility allows for curvature in relationships between soluble protein median fluorescence intensities and nonspecific binding median fluorescence intensities; 2) to stabilize correction, the fit of the nonlinear regression function is obtained via repeated cross-validation; and 3) the utility addresses possible bias due to technical error in measured nonspecific binding. The utility first logarithm transforms and then removes plate/batch/lot artifacts from median fluorescence intensities prior to correction for nonspecific binding, even when plates/batches/lots are unbalanced with respect to experimental factors of interest. Continuous (e.g., age) and categorical (e.g., diagnosis) covariates are accommodated in plate/batch/lot artifact correction. We present application of the utility to a panel of 62 cytokines in a sample of human patients diagnosed with systemic sclerosis and to an experiment that examined multiple lots of a human 51-cytokine panel. The R script for our new utility is publicly available for download from the web.