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Photometry (immunoturbidimetry)
Calprotectin is a biomarker used in the diagnosis of acute or chronic inflammatory bowel disease (IBD). It can serve as an additional non-invasive marker to support the diagnosis of IBD.
What is Calprotectin?
Calprotectin is a calcium-binding protein of the S100 family, predominantly found in neutrophilic granulocytes. During inflammatory processes, it is released in increased quantities. In gastrointestinal inflammation, calprotectin crosses the intestinal mucosa into the lumen and can therefore be detected in faeces. Measurement in faecal samples provides a non-invasive assessment of inflammatory activity within the gastrointestinal tract – a method well established in human medicine and increasingly applied in veterinary diagnostics.
Indications in Dogs
In dogs, faecal calprotectin is used as a marker for chronic inflammatory bowel disease. Elevated concentrations correlate with both the severity of histopathological changes and the clinical activity index (CCECAI). It can assist in differentiating inflammatory from non-inflammatory diarrhoea, assessing disease activity, and monitoring treatment response.
Calprotectin is particularly valuable for reflecting the severity of chronic enteropathy. Studies show that dogs with a high CCECAI (e.g. ≥ 12) exhibit significantly increased values. Higher faecal calprotectin concentrations are associated with a greater likelihood of requiring immunosuppressive therapy and may support prognostic evaluation. During follow-up, failure of calprotectin levels to normalise may indicate incomplete remission, while a renewed increase can precede clinical deterioration.
Points to Consider
As with all biomarkers, calprotectin is not disease-specific. It indicates the presence and magnitude of inflammation but not its cause. Elevated values may also occur in bacterial infections, parasitic infestations, or neoplastic disease. Interpretation must therefore be made within the clinical context and supported by additional diagnostics such as imaging, endoscopy, or histopathology.
Normal faecal calprotectin concentrations do not exclude enteropathy. This is particularly relevant in dogs, where the predominant inflammatory pattern is often lymphoplasmacytic rather than neutrophilic. Many canine enteropathies are also food-responsive, and in such cases, a strong neutrophilic response – and therefore elevated calprotectin – is not expected.
Calprotectin in Cats
Calprotectin has also shown promise in feline medicine and is used as a supportive marker in cases of chronic diarrhoea. Of particular interest is its potential role in distinguishing inflammatory from neoplastic processes (e.g. low-grade lymphoma). Faecal calprotectin concentrations may be significantly higher in lymphoma; however, a reliable diagnostic distinction has not yet been firmly established.
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