Development and analytical validation of a radioimmunoassay for the measurement of alpha1-proteinase inhibitor concentrations in feces from healthy puppies and adult dogs. Academic Article uri icon


  • 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.

published proceedings

  • J Vet Diagn Invest

altmetric score

  • 6

author list (cited authors)

  • Heilmann, R. M., Paddock, C. G., Ruhnke, I., Berghoff, N., Suchodolski, J. S., & Steiner, J. M

citation count

  • 26

complete list of authors

  • Heilmann, Romy M||Paddock, Casey G||Ruhnke, Isabelle||Berghoff, Nora||Suchodolski, Jan S||Steiner, Jörg M

publication date

  • May 2011