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 µg/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.