Calprotectin is a protein indicating inflammation within the intestines. Elevated levels can signal various gastrointestinal conditions. Analyzing calprotectin helps healthcare providers determine if inflammation is present and guides further diagnostic steps. This non-invasive biomarker offers insights into intestinal health. Its measurement provides an early indication of inflammatory processes, helping differentiate conditions requiring distinct management.
What is Calprotectin?
Calprotectin is a protein primarily found within neutrophils, a white blood cell playing a significant role in the body’s immune response. These cells are abundant and quickly migrate to sites of inflammation throughout the body. It accounts for up to 60% of the soluble protein content within the cytosol of neutrophils and is also found in monocytes and macrophages.
Upon activation or death, these neutrophils release calprotectin into the intestinal lumen. This released calprotectin then mixes with stool, making it detectable through a stool sample. The protein is stable in feces, resisting enzymatic degradation, which makes it a reliable marker for intestinal inflammation. Calprotectin also possesses antimicrobial properties by sequestering metal ions essential for bacterial and fungal growth.
The Calprotectin Test
Measuring calprotectin levels involves a non-invasive fecal calprotectin stool test. This test detects and quantifies calprotectin in a stool sample, reflecting intestinal inflammation. The laboratory analyzes the stool sample using methods like enzyme-linked immunosorbent assay (ELISA). Results are reported in micrograms per gram (µg/g) of stool.
Normal calprotectin levels are typically below 50 µg/g, though some guidelines use a threshold of up to 100 µg/g for adults. Levels between 50-200 µg/g are often considered borderline or slightly elevated, potentially warranting a repeat test. Elevated levels, generally above 200 µg/g or 250 µg/g, indicate active intestinal inflammation.
Causes of Elevated Calprotectin
Several conditions can lead to elevated calprotectin levels. Inflammatory Bowel Disease (IBD), encompassing Crohn’s disease and ulcerative colitis, is a primary cause of persistently high calprotectin. In IBD, the immune system attacks the digestive tract, leading to chronic inflammation, and calprotectin levels often correlate with disease severity. The fecal calprotectin test helps distinguish IBD from Irritable Bowel Syndrome (IBS), a non-inflammatory condition with typically normal or mildly elevated levels.
Gastrointestinal infections are another common cause. Bacterial, viral, or parasitic infections trigger an inflammatory response, causing neutrophils to release calprotectin. These elevations are usually temporary and resolve once the infection clears. Certain medications, particularly non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, can also cause intestinal irritation and inflammation. Discontinuing NSAID use for at least six weeks before a calprotectin test is often recommended to avoid false positive results.
Celiac disease, an autoimmune disorder triggered by gluten consumption, can also be associated with elevated calprotectin levels, especially in untreated cases. Calprotectin is not universally used for diagnosing or managing celiac disease, as its elevation can be inconsistent in adults. Other conditions that may lead to elevated calprotectin include diverticulitis, microscopic colitis, and in some instances, colorectal cancer.
What Happens After an Elevated Result?
An elevated calprotectin result suggests intestinal inflammation but is not a definitive diagnosis. The next steps involve further investigation to pinpoint the exact cause. A healthcare provider will evaluate the calprotectin level alongside a person’s symptoms, medical history, and other diagnostic findings.
Often, an elevated result leads to a referral to a gastroenterologist. This specialist may recommend more invasive diagnostic procedures, such as a colonoscopy with biopsies. Endoscopy allows for direct visualization of the intestinal lining and collection of tissue samples, providing a definitive diagnosis for conditions like IBD. The calprotectin test can help avoid unnecessary colonoscopies in individuals whose symptoms are more likely due to non-inflammatory conditions like IBS.
For individuals diagnosed with IBD, calprotectin testing monitors disease activity and treatment effectiveness. Levels can indicate whether the disease is in remission or experiencing a flare-up, guiding therapy adjustments. Regular monitoring can help predict potential relapses, allowing for proactive management to maintain long-term intestinal health.