Interpretation
CLINICAL INFORMATION
Calprotectin, a member of the S100 calcium-binding protein family 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. Neutrophils are then activated, leading to release of calprotectin which is eventually translocated across the epithelial barrier and enters the lumen of the gut.
As inflammation progresses, the released calprotectin is absorbed by faecal material before it is excreted from the body. The amount of calprotectin present in the faeces is proportional to the number of neutrophils within the gastrointestinal mucosa and can be used as an indirect marker of intestinal inflammation.
Calprotectin is most frequently used as part of the diagnostic evaluation of patients with suspected inflammatory bowel disease (IBD) including Crohns disease and ulcerative colitis. Although distinct in their pathology and clinical manifestations, both are associated with significant intestinal inflammation. Elevated concentrations of faecal calprotectin may be useful in distinguishing IBD from functional gastrointestinal disorders, such as irritable bowel syndrome.
In this context, faecal calprotectin has sensitivity and specificity of approximately 85%. However, although increases in faecal calprotectin are not diagnostic for IBD, as other disorders such as coeliac disease, colo-rectal cancer, and gastrointestinal infections, may also be associated with neutrophilic inflammation.
INTERPRETATION
Calprotectin concentrations below 50.0 ug/g are not suggestive of an active inflammatory process within the gastrointestinal system and serve as a good ‘rule-out’ test. In this context, for patients experiencing gastrointestinal symptoms, consider further evaluation for functional gastrointestinal disorders.
Much higher calprotectin concentrations are suggestive of an active inflammatory process within the gastrointestinal system. Additional diagnostic testing to determine the aetiology is appropriate.
For patients with known inflammatory bowel disease in remission, faecal calprotectin >50 µg/g is associated with an increased risk of relapse over the next 12 months.
ADULTS
Faecal calprotectin test helps to differentiate inflammatory bowel disease (IBD) from irritable bowel syndrome with lower gastrointestinal symptoms of more than 6 weeks duration when specialist referral is being considered. With symptoms of less than 6 weeks duration, there is poorer specificity for IBD. Calprotectin cannot distinguish ulcerative colitis from Crohns disease.
CHILDREN
Faecal calprotectin helps to differentiate inflammatory bowel disease from non-inflammatory bowel disease who have been referred to specialists for investigation.
In children less than 4 years old, there is overlap of results from normal children with those having various paediatric gastrointestinal pathologies, rendering a positive test (greater than 50 ug/g) very non-specific especially if the result falls within the crude age-related range. Results should be interpreted with caution.
CAUTIONS
Elevations in faecal calprotectin are not diagnostic for inflammatory bowel disease (IBD), and normal faecal 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 faecal calprotectin may be observed in patients taking nonsteroidal anti-inflammatory drugs, aspirin, or proton-pump inhibitors.
Elevations in faecal calprotectin may be observed in other conditions associated with neutrophilic inflammation of the gastrointestinal system, including coeliac disease, colorectal cancer, and gastrointestinal infections.
Falsely decreased concentrations of faecal calprotectin may be observed in patients with neutropenia or granulocytopenia.
Reference Intervals
Reference Interval <50 ug/g
Samples with calprotectin levels greater than the working range of the assay will be reported as >800 ug/g.
Please contact the laboratory if a more accurate quantitative result is required above 800 ug/g
