Calprotectin is a protein that specialized white blood cells, known as neutrophils, produce in response to inflammation. When inflammation occurs within the intestines, these neutrophils travel to the affected site and release calprotectin, which then mixes with stool. A fecal calprotectin test is a non-invasive analysis that measures the concentration of this protein in a stool sample to detect the presence and extent of intestinal inflammation.
Interpreting High Calprotectin Levels
A high fecal calprotectin result indicates that there is active inflammation somewhere in the gastrointestinal tract. The degree of elevation corresponds to the severity of the inflammation. While specific numerical ranges can vary between laboratories, results are categorized. Levels below 50 micrograms per gram (μg/g) are considered normal, suggesting no significant inflammation.
Results falling into a borderline range, between 50 and 200 μg/g, may suggest mild inflammation or a condition that is worsening. In these cases, a doctor might recommend repeating the test after a few weeks to observe any changes. Levels above 200-250 μg/g are considered high and strongly point toward active intestinal inflammation, warranting further investigation.
The main function of this test is to help doctors differentiate between inflammatory and non-inflammatory conditions that share similar symptoms. For example, it helps distinguish Inflammatory Bowel Disease (IBD) from functional disorders like Irritable Bowel Syndrome (IBS), which does not cause inflammation.
Primary Causes of Elevated Calprotectin
The most significant cause of very high calprotectin levels is Inflammatory Bowel Disease (IBD). IBD encompasses a group of chronic conditions that cause prolonged inflammation of the digestive tract. The two main forms of IBD are Crohn’s disease, which can affect any part of the gastrointestinal tract from the mouth to the anus, and ulcerative colitis, which is limited to the colon and rectum. In newly diagnosed IBD, calprotectin concentrations can be particularly high.
Other conditions can also lead to elevated calprotectin. Bacterial or parasitic infections in the gut are common culprits, as the body’s immune response causes inflammation. These elevations are temporary and resolve once the infection is treated.
Celiac disease, an immune reaction to eating gluten, can cause inflammation and lead to high calprotectin levels. Less frequently, significant inflammation can be caused by colorectal polyps or, in some cases, colorectal cancer.
Factors That Can Influence Test Results
Certain medications and activities can temporarily increase calprotectin levels, even in the absence of a chronic disease. The use of non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, is a well-known factor. These medications can cause irritation and low-grade inflammation in the intestinal lining, leading to a rise in calprotectin.
Recent gastrointestinal infections that have since resolved can also cause lingering inflammation that keeps calprotectin levels elevated for a short period. Strenuous physical exercise has also been observed to cause a temporary increase in some individuals. Inflammation from sources outside the gut, such as a dental abscess, can sometimes have an effect, though this is less common.
Next Steps After a High Result
Receiving a high fecal calprotectin result is an indicator for further action, not a final diagnosis. The first step is to discuss the results with a doctor, who may refer you to a gastroenterologist for specialized evaluation. The specialist will consider the calprotectin level in the context of your specific symptoms and medical history.
To determine the underlying cause of the inflammation, further diagnostic tests are required. This often involves blood tests to check for other markers of inflammation or nutritional deficiencies. The most definitive follow-up procedure is an endoscopy, such as a colonoscopy or sigmoidoscopy, which allows the doctor to visually inspect the lining of the intestines and collect small tissue samples (biopsies) for analysis to confirm a diagnosis.
Once a diagnosis is established and treatment begins, the fecal calprotectin test may be used again. It is also used for monitoring the condition and assessing how well a treatment is working to control inflammation. A decrease in calprotectin levels over time indicates that the treatment is effective and mucosal healing is occurring.