Chemometric analysis of attenuated total reflectance infrared spectral data for quantitation of immunoglobulin G in equine plasma and serum

• Chemometric analysis of infrared spectra to build calibration curves for immunoglobulin G`

Immunoglobulin G (IgG) is a crucial antibody to protect animals from invasion by microorganisms. Although there exist several methods in veterinary medicine to measure IgG levels for diagnostic and therapeutic purposes, these methods suffer from various weaknesses. Infrared (IR) spectroscopy coupled with chemometric tools such as principal component regression has been widely employed for the measurement of compounds in mixtures with the advantages that include simplicity, quickness and low test cost. Earlier investigation for IgG assay based on transmission IR spectroscopy using laboratory grade equipment has been conducted, but it is not readily transferrable to the clinic, hospital or small laboratory setting. More robust attenuated total reflectance (ATR) IR spectroscopy platforms have recently been developed for a range of roles in the field. This study investigated the possibility of using ATR-IR spectroscopy to determine the IgG concentrations in foal serum and adult horse plasma samples. The results of this work showed that immunoglobulin G concentrations predicted by ATR-IR spectroscopy with chemometric analysis had good agreement with those obtained from the radial immunodiffusion (RID) reference method. The precision of this approach was most compatible to RID method when the IgG concentration was high, but poorer for lower IgG concentrations. It was also showed that building a united calibration model for serum and plasma samples is likely. The results of this work indicate that ATR-IR spectroscopy coupled with chemometric analysis is a promising technique to measure the equine serum and plasma IgG concentrations in the veterinary clinical or hospital environment.