Analytical validation of an enzyme-linked immunosorbent assay for the quantification of S100A12 in the serum and feces of cats

Background Measuring S100A12 concentrations in serum and feces is a sensitive and specific marker of inflammation, such as seen with chronic gastrointestinal inflammation in people and dogs. Biomarkers of inflammation in cats are currently lacking. Objectives We aimed to analytically cross-validate the canine S100A12-ELISA for the measurement of S100A12 in feline specimens. Methods The ELISA was analytically validated by assessing dilutional linearity, spiking/recovery, intra- and inter-assay variability. Reference intervals for serum and fecal feline S100A12 concentrations were calculated using samples from healthy cats, and the short-term biological variation of fecal S100A12 was assessed. Results Observed-to-expected ratios (O/E) for serial dilutions of serum and fecal extracts ranged from 91%-159% (mean, 120%) and 100%-128% (mean, 114%), and for the spiking/recovery method ranged from 106%-263% (mean, 154%) and 52%-171% (mean, 112%). Intra- and inter-assay CV% for serum were <= 5.6% and <= 14.0%, and for fecal extracts were <= 3.8% and <= 19.1%, repsectively. RIs for feline serum and fecal S100A12 concentrations were <43 mu g/L and < 20 ng/g, respectively. A mild short-term biologic variation, but large individuality were detected when measuring fecal S100A12 concentrations in healthy cats. Conclusions The canine S100A12-ELISA is accurate, reproducible, and sufficiently linear and precise for the measurement of S100A12 in feline serum and fecal samples. The use of this assay is a reasonable option for the measurement of S100A12 concentrations in feline specimens and provides a basis for the further evaluation of S100A12 in cats with gastrointestinal disease. Using a population-based RI for fecal feline S100A12 appears to be of limited value.