Development and analytical validation of a radioimmunoassay for the quantification of alpha1 -proteinase inhibitor in serum and feces from the common marmoset (Callithrix jacchus).

BACKGROUND: The objective of this study was to develop and analytically validate a radioimmunoassay (RIA) for the measurement of alpha1 -proteinase inhibitor (α1 -PI) concentrations in serum and feces from the common marmoset.
METHODS: Serum samples (n = 30) and 3-day fecal samples (n = 30) were obtained from healthy marmosets. An RIA was established and validated by determination of sensitivity, working range, dilutional parallelism, spiking recovery, and intra- and interassay variability. A reference interval for mα1 -PI in serum and feces was established.
RESULTS: Sensitivity and upper limit of the working range were 0.75 and 100.62 μg/L, respectively. Observed-to-expected (O/E) ratios for serial dilutions ranged from 89.9% to 123.0% (mean ±SD: 106.0 ± 11.5%) for 8 serum samples, and from 90.6% to 132.7% (mean ±SD: 107.6 ± 19.2%) for 4 fecal samples. O/E ratios for spiking recovery ranged from 97.6% to 104.4% (mean ±SD: 101.3 ± 3%) for 4 serum samples, and from 97.5% to 101.4% (mean ±SD: 99.2 ± 1.8%) for 4 fecal samples and 3 different spiking concentrations. Coefficients of variation (CV) for intra-assay variability for 8 serum samples ranged from 1.7% to 10.6% and 2.2% to 5.1% in the 8 fecal samples. The interassay CV for eight serum samples ranged from 1.3% to 9.9%, and from 1.0% to 6.7% in the 8 fecal samples. The reference interval in serum was determined to be 1047-1484 μg/L. The reference interval in serum was determined to be 1047-1484 μg/L. The reference interval for the 3-day mean fecal concentration, and 3-day maximum fecal concentration were determined to be 32.4-124.4 μg/g and 39.1-158.7 μg/g of feces, respectively.
CONCLUSION: The developed assay is sensitive, linear, accurate, precise, and reproducible. Further studies are needed to determine the clinical utility of this assay.