Feline Fecal Calprotectin Quantification

Calprotectin was measured in all fecal extracts using the fCal turbo assay on a Roche Cobas 311 chemistry analyzer as previously validated for feline specimens [43 (link)]. Briefly, fecal extracts were incubated with proprietary reaction buffer and mixed with polystyrene nanoparticles that had been pre-coated with polyclonal anti-human calprotectin antibodies. Agglutination by binding of fCal increases sample turbidity and was measured at 546 nm and 800 nm, and the fCal concentration was determined by interpolation from the calibration curve [42 ,43 (link)]. The assay has a working range from 3–2000 μg/g for feline samples, and samples with a fCal concentration >2000 μg/g were re-assayed in a 1:1000 dilution.