Abstract
The objective of this study was to develop and compare the performance of laboratory grade and portable attenuated total reflectance infrared (ATR-IR) spectroscopic approaches in combination with partial least squares regression (PLSR) for the rapid quantification of alpaca serum IgG concentration, and the identification of low IgG (<1000 mg/dL), which is consistent with the diagnosis of failure of transfer of passive immunity (FTPI) in neonates. Serum samples (n = 175) collected from privately owned, healthy alpacas were tested by the reference method of radial immunodiffusion (RID) assay, and laboratory grade and portable ATR-IR spectrometers. Various pre-processing strategies were applied to the ATR-IR spectra that were linked to corresponding RID-IgG concentrations, and then randomly split into two sets: calibration (training) and test sets. PLSR was applied to the calibration set and calibration models were developed, and the test set was used to assess the accuracy of the analytical method. For the test set, the Pearson correlation coefficients between the IgG measured by RID and predicted by both laboratory grade and portable ATR-IR spectrometers was 0.91. The average differences between reference serum IgG concentrations and the two IR-based methods were 120.5 mg/dL and 71 mg/dL for the laboratory and portable ATR-IR-based assays, respectively. Adopting an IgG concentration <1000 mg/dL as the cut-point for FTPI cases, the sensitivity, specificity, and accuracy for identifying serum samples below this cut point by laboratory ATR-IR assay were 86, 100 and 98%, respectively (within the entire data set). Corresponding values for the portable ATR-IR assay were 95, 99 and 99%, respectively. These results suggest that the two different ATR-IR assays performed similarly for rapid qualitative evaluation of alpaca serum IgG and for diagnosis of IgG <1000 mg/dL, the portable ATR-IR spectrometer performed slightly better, and provides more flexibility for potential application in the field.
Highlights
Immunoglobulins are glycoproteins produced by B-lymphocytes, and are a crucial component of the host’s adaptive immune system [1]
The objective of the present study was to investigate the feasibility and compare the performance of laboratory grade and portable attenuated total reflectance infrared (ATR-IR) spectrometers combined with multivariate analysis (PLSR) for the rapid quantification of alpaca serum Immunoglobulin G (IgG) concentrations and the identification of low IgG (
Serum IgG determined by radial immunodiffusion (RID) method
Summary
Immunoglobulins are glycoproteins produced by B-lymphocytes, and are a crucial component of the host’s adaptive immune system [1]. Camelids have an epitheliochorial microcotyledonary placenta that does not allow the transplacental transfer of immunoglobulins from the dam to the fetus [2]. Newborn camelids are born essentially hypogammaglobulinemic and rely on the transfer of immunoglobulins through colostrum intake and enteric absorption for passive immunity [2, 3]. Immunoglobulin G (IgG) is the predominant class of colostral immunoglobulins involved in the transfer of passive immunity to newborn crias [4]. Early and accurate diagnosis of FTPI in camelids is an integral part of most camelid husbandry programs that can reduce morbidity and mortality rates for crias [9]
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