Overview
Calprotectin is a calcium- and zinc-binding protein released predominantly by neutrophils during inflammatory processes in the gastrointestinal tract. The presence of calprotectin in stool reflects neutrophil migration into intestinal tissue, making fecal calprotectin a reliable biomarker of intestinal inflammation. Measurement of stool calprotectin provides a non-invasive and quantitative assessment of gut inflammation and is widely used in the evaluation of gastrointestinal disorders.
Fecal calprotectin is particularly valuable in differentiating inflammatory bowel disease (IBD) from irritable bowel syndrome (IBS) and other functional gastrointestinal disorders. While it does not identify the specific cause or etiology of inflammation, it serves as an important tool for monitoring disease activity, treatment response, and flare-ups in patients with IBD. The test is commonly performed using a quantitative chemiluminescent immunoassay (CLIA) method and requires proper stool sample collection and refrigerated storage to ensure accuracy. Calprotectin (Stool)
Symptoms
Stool calprotectin testing is indicated in patients presenting with gastrointestinal symptoms suggestive of intestinal inflammation. These symptoms include persistent bloody or watery diarrhea, abdominal cramps, and gastrointestinal discomfort lasting for more than a few days, with or without fever. Elevated calprotectin levels are associated with active inflammatory conditions of the gut.
Very high levels of calprotectin are commonly seen in inflammatory bowel disease and bacterial food poisoning. Moderately elevated levels may be observed in intestinal or colorectal cancer, celiac disease, Clostridium difficile infections, and in patients using non-steroidal anti-inflammatory drugs (NSAIDs). Treated or partially controlled IBD may also show somewhat elevated values. In contrast, low calprotectin levels are typically seen in IBS, viral gastroenteritis, healthy individuals, remission phases of IBD, postoperative IBD with normal anatomy, and non-inflammatory diarrhea.
Causes
Elevated stool calprotectin levels result from neutrophil-driven inflammation within the gastrointestinal mucosa. The most common cause is inflammatory bowel disease, including Crohn’s disease and ulcerative colitis. Acute bacterial infections causing food poisoning also lead to marked elevations.
Other causes of increased calprotectin include colorectal and intestinal malignancies, celiac disease, Clostridium difficile infections, and medication-related inflammation, particularly from NSAID use. Even in treated IBD, residual mucosal inflammation can result in persistently elevated calprotectin levels. Conversely, low levels indicate the absence of significant neutrophilic inflammation and are usually associated with functional gastrointestinal disorders rather than organic disease.
Risk Factors
Individuals with known or suspected inflammatory bowel disease are at higher risk of having elevated stool calprotectin levels. Patients experiencing recurrent gastrointestinal symptoms such as chronic diarrhea, abdominal pain, or unexplained gastrointestinal bleeding are also more likely to show abnormal results.
Use of NSAIDs is a recognized risk factor for false-positive elevations due to drug-induced intestinal inflammation. Gastrointestinal infections, colorectal malignancies, and improper sample handling or timing can influence test results. Variability may also arise from patient-related factors and inconsistent adherence to sample collection and testing protocols. Due to these factors, serial measurements are often necessary for reliable interpretation.
Prevention
While stool calprotectin itself is a diagnostic and monitoring tool rather than a preventable condition, appropriate clinical use can help prevent unnecessary invasive procedures. Proper sample collection is essential, involving the transfer of approximately 5 grams of stool into an unpreserved container, followed by refrigerated storage to maintain sample integrity.
Regular monitoring of calprotectin levels in patients with IBD aids in early detection of disease flares, assessment of treatment response, and prediction of relapse before clinical symptoms appear. Judicious use of NSAIDs, timely evaluation of gastrointestinal infections, and adherence to testing guidelines help minimize false-positive results. Using stool calprotectin as a screening and monitoring tool can reduce the need for invasive investigations such as colonoscopy when results are normal, supporting safer and more cost-effective patient care.
