Idiopathic IBD of dogs is an important disorder, which is characterized by chronic gastrointestinal signs, such as loose feces, diarrhea, and weight loss. In many dogs, IBD poses a diagnostic challenge. No single criterion-referenced diagnostic test is currently available for the diagnosis of IBD or for assessment of severity or activity of IBD. Commonly, a combination of clinical signs, laboratory variables, and endoscopic and histologic findings is used for diagnosing and monitoring IBD in canine patients.1–3 Because the clinical signs are highly variable at various stages of the disease, a clinical scoring system has been proposed in 1 study4 and expanded in another study.3 A consensus for the classification of IBD on the basis of endoscopic and histologic criteria is still lacking and is currently being developed by the gastrointestinal standardization group of the World Small Animal Veterinary Association.
Laboratory markers represent objective measures for the assessment of gastrointestinal tract disorders. They are noninvasive or minimally invasive and simple to perform. Only a few immunologic and inflammatory markers have been correlated with clinical IBD activity in canine patients. Serum C-reactive protein, an acutephase reactant and nonspecific inflammatory marker, can be useful as a prognostic marker for IBD.1,4 However, in some studies,3,5 C-reactive protein did not reflect the severity of IBD in canine patients as assessed by clinical scores (eg, canine IBD activity index) or histologic grade. Other inflammatory markers for IBD in dogs have been studied less extensively or are less useful than is C-reactive protein.1,4,5 Hence, there is a need for novel laboratory markers that will aid in the management of dogs with IBD.
Calprotectin, a heterodimeric protein complex that binds Ca2+ and Zn2+ and has antimicrobial activity, is abundant in PMNs and macrophages. Calprotectin is contained in infiltrating myelomonocytic cells at sites of inflammation, where it is actively or passively released into the extracellular space as a result of cell disintegration.6,7 Epithelial cells (eg, keratinocytes) also express calprotectin after inflammatory activation or malignant transformation. In humans, increases in serum or plasma concentrations of calprotectin have been associated with various infectious and inflammatory conditions, autoimmune disorders, and malignancies.6,8 Because it reflects the phagocyte turnover in vivo, calprotectin has been used as an extremely sensitive but nonspecific inflammatory marker that correlates with local and systemic signs of disease activity.6,8,9 Serum calprotectin concentrations can be used to discriminate between active and quiescent Crohn's disease and are believed to be useful for the monitoring of clinical disease activity in humans with Crohn's disease.10
Increased fecal concentrations of calprotectin in patients with Crohn's disease and ulcerative colitis have been correlated with disease activity, as determined by use of endoscopy, histologic examination, and excretion of iodineradiolabeled PMNs.11,12 Increased fecal concentrations of calprotectin have also been associated with gastrointestinal neoplasms, infections, polyps, and the use of nonsteroidal anti-inflammatory agents.12,13 Measurement of fecal calprotectin concentrations is simple to perform and widely used in human medicine as a diagnostic screening test, for monitoring treatment response and predicting clinical relapse in patients with IBD, and for discriminating organic from nonorganic intestinal disease (such as irritable bowel syndrome).14–16
An immunoassay for calprotectin measurement is currently available only for humans. Therefore, the objectives of the study reported here were to develop and analytically validate an RIA for the quantification of cCP in canine serum and fecal extracts and to evaluate the potential use of cCP concentrations as a clinical marker in dogs with IBD.
Value for the zero-standard tube
Ratio of the value for the zero-standard tube to the total counts for the tracer tube
Bovine serum albumin
Counts per minute
Coefficient of variation
Sodium iodide I 125
Inflammatory bowel disease
Nonspecific binding value
Polymorphonuclear neutrophilic leukocyte
Total counts for the tracer tube
Fecal collection tube (101 × 16.5 mm; including spatula), Sarstedt AG & Co, Nümbrecht, Germany.
Complete EDTA-free proteinase inhibitor cocktail tablets, Roche Diagnostics GmbH, Mannheim, Germany.
Fisherbrand serum filter system (IB model), Fisher Scientific Inc, Pittsburgh, Pa.
Heilmann RM, Suchodolski JS, Steiner JM, et al. Purification and partial characterization of canine calprotectin (abstr), inProceedings. 25th Annu Am Coll Vet Intern Med Forum 2007;849.
PD-10 desalting column (1.5 × 5 cm), GE Healthcare Bio-Sciences Inc, Piscataway, NJ.
Corning polypropylene tubes, Fisher Scientific Inc, Pittsburgh, Pa.
HiTrap NHS-activated HP, GE Healthcare Bio-Sciences Inc, Piscataway, NJ.
NuPAGE (10% Bis/Tris), Invitrogen, Carlsbad, Calif.
Immunodiffusion plates (agarose gelling), Pierce, Rockford, Ill.
Coomassie Plus, Pierce, Rockford, Ill.
Rabbit serum (sterile-filtered), Sigma-Aldrich Co, St Louis, Mo.
Precipitating solution (N6), Diagnostic Products Corp, Los Angeles, Calif.
Wallac 1470 WIZARD, PerkinElmer Life and Analytical Sciences Inc, Wellesley, Mass.
GraphPad Prism, version 5.0, GraphPad Software Inc, San Diego, Calif.
Tissue grinder Polytron PTMR-2100, Kinematica, Littau, Switzerland.
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Johne B, Fagerhol MK, Lyberg T, et al. Functional and clinical aspects of the myelomonocyte protein calprotectin. Mol Pathol 1997;50:113–123.
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