Calprotectin is a protein found in white blood cells, specifically neutrophils, which are part of the body’s immune system. When inflammation occurs, particularly within the gastrointestinal tract, these neutrophils migrate to the inflamed area and release calprotectin. Measuring the level of calprotectin in a stool sample serves as a non-invasive indicator of intestinal inflammation. This test helps healthcare providers understand if symptoms are due to inflammation or other causes.
What Calprotectin Is and Its Purpose
Calprotectin is primarily released by neutrophils. When the intestinal immune system is activated due to inflammation, these cells accumulate at the site. The release of calprotectin into the gut lumen makes it detectable in stool. The quantity of calprotectin found in feces correlates with the number of neutrophils present in the gastrointestinal lining, acting as an indirect marker of intestinal inflammation.
The calprotectin test is particularly useful for distinguishing between inflammatory conditions, such as inflammatory bowel disease (IBD), and non-inflammatory conditions, like irritable bowel syndrome (IBS). It also helps monitor disease activity in individuals already diagnosed with IBD. The non-invasive nature of the stool test makes it a valuable screening tool.
Interpreting Calprotectin Levels
Understanding calprotectin test results involves recognizing typical reference ranges, though thresholds vary between laboratories. A fecal calprotectin concentration below 50 micrograms per gram (µg/g) is considered normal, suggesting the absence of significant active inflammation. This level indicates gastrointestinal symptoms are likely due to functional disorders rather than inflammation.
Levels between 50 µg/g and 120 µg/g are considered borderline. This range suggests a mild inflammatory process, potentially seen in treated IBD or associated with nonsteroidal anti-inflammatory drugs (NSAIDs). For individuals with symptoms suggestive of IBD, repeat testing in 4 to 6 weeks may be recommended.
A calprotectin concentration above 120 µg/g suggests an active inflammatory process. Levels over 200 µg/g or 250 µg/g indicate significant inflammation. Very high levels, exceeding 500 µg/g or 600 µg/g, strongly indicate active and significant inflammation, often seen in conditions like IBD. Higher values correlate with a greater degree of inflammation.
Underlying Causes of High Calprotectin
Elevated calprotectin levels primarily indicate the presence of inflammation in the gastrointestinal tract, but they are not specific to a single condition. Inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, are common and significant causes of very high calprotectin levels. In IBD, the protein is released as neutrophils and other immune cells gather at sites of chronic inflammation in the gut.
However, high calprotectin can also result from other, less severe or temporary conditions. Gastrointestinal infections caused by bacteria, viruses, or parasites can trigger an inflammatory response that elevates calprotectin levels. Levels tend to be notably higher in bacterial infections compared to viral ones.
Other causes of elevated calprotectin include:
- Non-steroidal anti-inflammatory drugs (NSAIDs), which can irritate the gut lining.
- Diverticulitis, an inflammation of pouches in the colon.
- Microscopic colitis.
- Celiac disease.
- Colorectal cancer, where inflammation may occur around cancerous tissue.
It is important to understand that a high calprotectin result indicates inflammation and the need for further investigation, rather than automatically diagnosing a specific disease like IBD.
What to Do After a High Result
Receiving a high calprotectin result necessitates further medical evaluation by a healthcare professional, typically a gastroenterologist. This test is a screening tool that points to inflammation, but it does not provide a definitive diagnosis on its own. The doctor will consider the calprotectin level in conjunction with a patient’s symptoms, medical history, and other clinical findings.
Common follow-up diagnostic tests may include an endoscopy, such as a colonoscopy or gastroscopy, often with biopsies to examine tissue samples directly. Imaging studies like MRI or CT scans may also be recommended to visualize the gastrointestinal tract. Additional blood tests could be performed to assess other markers of inflammation or nutritional status.
Discussing your specific results and symptoms with your doctor is important to determine the appropriate course of action. The goal of these further investigations is to identify the underlying cause of the inflammation and establish an accurate diagnosis. This comprehensive approach ensures that the correct treatment plan can be developed.