CALPROTECTIN
PURPOSE
- Evaluation of patients suspected of having a GIT inflammatory process
- Distinguishing inflammatory bowel disease (IBD) from irritable bowel syndrome (IBS), when used in conjunction with other diagnostic modalities, including endoscopy, histology, and imaging
Clinical information:
- Calprotectin is expressed primarily by granulocytes and, to a lesser degree, by monocytes/macrophages and epithelial cells.
- In neutrophils, calprotectin comprises almost 60% of the total cytoplasmic protein content.
- Activation of the intestinal immune system leads to recruitment of cells from the innate immune system, including neutrophils >>> The neutrophils are then activated >>> which leads to release of cellular proteins, including calprotectin.
Calprotectin eventually translocates across the epithelial barrier and enters the lumen of the gut.
- As the inflammatory process progresses, the released calprotectin is absorbed by the fecal material before it is excreted from the body.
- The amount of calprotectin present in the feces is proportional to the number of neutrophils within the GIT mucosa and can be used as an indirect marker of intestinal inflammation.
_ Patients with IBD may be diagnosed with Crohn disease or ulcerative colitis.
When used for this differential diagnosis, fecal calprotectin has sensitivity and specificity both of approximately 85%. However, it must be remembered that increases in fecal calprotectin are not diagnostic for IBD, as other disorders such as celiac disease, colorectal cancer, and GIT infections, may also be associated with neutrophilic inflammation.
REFERENCE VALUES
< or =50.0 ug/g (Normal)
50.1-120.0 ug/g (Borderline)
> or =120.1 ug/g (Abnormal)
Reference values apply to all ages.
Interpretattion:
- Calprotectin concentrations of 50.0 ug/g and lower are not suggestive of an active inflammatory process within the GIT. For patients experiencing GIT symptoms, consider further evaluation for functional GIT disorders.
- Calprotectin concentrations between 50.1 and 120.0 ug/g are borderline and may represent a mild inflammatory process, such as in treated IBD or associated with NSAID or aspirin usage. For patients with clinical symptoms suggestive of IBD, retesting in 4 to 6 weeks may be indicated.
- Calprotectin concentrations of 120.1 ug/g and higher are suggestive of an active inflammatory process within the GIT. Further diagnostic testing to determine the etiology of the inflammation is suggested.
Causions:
- Elevations in fecal calprotectin are not diagnostic for IBD, and normal fecal calprotectin concentrations do not exclude the possibility of IBD. Diagnosis of IBD should be based on clinical evaluation, endoscopy, histology, and imaging studies.
- Borderline results in fecal calprotectin may be observed in patients taking NSAIDs, aspirin, or proton-pump inhibitors.
- For borderline results, repeat testing in 4 to 6 weeks is suggested.
- Elevations in fecal calprotectin may be observed in other disease states associated with neutrophilic inflammation of the GIT, including celiac disease, colorectal cancer, and GIT infections.
- Falsely decreased concentrations of fecal calprotectin may be observed in patients with neutropenia or granulocytopenia.
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