Development and analytical validation of an enzyme-linked immunosorbent assay (ELISA) for the measurement of alpha1-proteinase inhibitor in serum and faeces from cats

Abstract The objective of this study was to develop and analytically validate an ELISA for the measurement of alpha 1 -proteinase inhibitor (α 1 -PI) in serum and faeces from cats. Lower detection limit, linearity, accuracy, precision, reproducibility, and reference intervals were determined. The lower detection limits were 0.02 g/L for serum and 0.04 μg/g for faeces. The observed-to-expected (O/E) ratios for serial dilutions of serum and faecal samples ranged from 100.0 to 129.7% (mean ± SD: 112.2 ± 9.9%) and 103.5 to 141.6% (115.6 ± 12.8%), respectively. The O/E ratios for samples spiked with seven known concentrations of α 1 -PI ranged from 82.3 to 107.8% (94.7 ± 7.6%) for serum, and 78.5 to 148.7% (96.8 ± 18.2%) for faeces. The coefficients of variation for intra-assay and inter-assay variability were