Calprotectin is a protein that binds to both calcium and zinc. Fecal calprotectin levels are abnormally increased in people with intestinal inflammation, thus it is useful for distinguishing between inflammatory and non-inflammatory diarrhea. Specifically, this test may be helpful in differentiating between inflammatory bowel disease and irritable bowel syndrome—calprotectin levels would be higher in the former disease and normal in the latter. Calprotectin is produced mostly from neutrophils and monocytes, which are immune system cells. These cells proliferate and accumulate in areas of inflammation. Thus, calprotectin levels are a marker of neutrophil activity. Calprotectin levels less than 50 mcg/g suggests that there is no inflammatory process occurring in the colon. Levels above 120 mcg/g almost certainly reflect some sort of inflammatory process in the large intestine. Readings between 50 and 120 mcg/g are considered borderline, which means a mild inflammatory process may be present. Borderline readings may occur in people taking daily doses of NSAIDs, proton pump inhibitors, or aspirin. Further workup is usually needed for people with borderline or abnormal calprotectin levels.
Normal Ranges for Calprotectin:
< or =50.0 mcg/g (Normal)
50.1-120.0 mcg/g (Borderline)
> or =120.1 mcg/g (Abnormal)
Calprotectin levels cannot be too low. A reading of zero would be considered normal.
Calprotectin is an indication of neutrophil activity. Neutrophil is a white blood cell that participates in inflammatory processes. Thus, high levels of calprotectin in the stool are often associated with inflammatory processes in the bowel such as inflammatory bowel disease. However, any state that increases neutrophil inflammation will lead to increased levels of calprotectin. Borderline result should be repeated in 4 to 6 weeks.
Some specific causes of high calprotectin levels are:
- Crohn's disease
- Ulcerative colitis
- Celiac disease
- Colorectal cancer
- Gastrointestinal infections
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