Development and analytical validation of a radioimmunoassay for the measurement of alpha1-proteinase inhibitor concentrations in feces from healthy puppies and adult dogs.
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Canine α(1)-proteinase inhibitor (cα(1)-PI), a proteolysis-resistant protein with a molecular weight similar to albumin, has been shown to be clinically useful as a marker for gastrointestinal protein loss in dogs. A competitive, liquid-phase radioimmunoassay was developed and analytically validated. Fecal samples were collected from 101 healthy pet dogs of various breeds and ages, and fecal cα(1)-PI (Fcα(1)-PI) concentrations were compared between dogs of different age groups. A reference interval for Fcα(1)-PI concentration was calculated using the central 95th percentile. Analytical sensitivity of the assay was 2.2 µg Fcα(1)-PI/g feces. Observed-to-expected ratios for the serial dilution and spiking recovery of 9 and 6 fecal extracts ranged from 90.4 to 152.0% and from 71.3 to 112.3%, respectively. Coefficients of variation for intra- and interassay variability for 6 fecal extracts were ≤10.8% and ≤12.5%, respectively. The reference intervals for the mean and maximum Fcα(1)-PI from fecal samples collected on 3 consecutive days were 2.2-13.9 µg/g and 2.2-21.0 µg/g, respectively. Fcα(1)-PI was significantly higher in dogs <1 year of age (P < 0.0001 for both mean and maximum Fcα(1)-PI for the 3 samples). The radioimmunoassay described is sensitive, linear, precise, reproducible, and accurate for clinical use, thus allowing reliable quantification of Fcα(1)-PI in clinical patients. Using this assay, a mean or a maximum Fcα(1)-PI for 3 sampling days of >13.9 µg/g or >21.0 µg/g, respectively, should be considered abnormal in dogs >1 year of age. Fecal cα(1)-PI concentrations in dogs <1 year of age were significantly higher and should be carefully interpreted in this age group.
author list (cited authors)
Heilmann, R. M., Paddock, C. G., Ruhnke, I., Berghoff, N., Suchodolski, J. S., & Steiner, J. M
complete list of authors
Heilmann, Romy M||Paddock, Casey G||Ruhnke, Isabelle||Berghoff, Nora||Suchodolski, Jan S||Steiner, Jörg M