Calprotectin is a protein commonly measured in stool samples to detect inflammation, particularly within the gastrointestinal tract. Elevated levels of this protein often signal the presence of inflammation, which can stem from various underlying causes. While inflammatory bowel diseases are frequent culprits, infections also represent a significant factor contributing to increased calprotectin levels. Understanding the different conditions that can lead to such elevations helps clarify the implications of a calprotectin test result.
Understanding Calprotectin
Calprotectin is a protein primarily released by white blood cells called neutrophils. These neutrophils, part of the immune system, migrate to inflamed or infected areas. When inflammation occurs in the intestines, neutrophils accumulate and release calprotectin into the gut lumen.
This protein is resistant to enzymatic degradation, remaining stable in stool, which makes it a reliable marker for intestinal inflammation. Measuring calprotectin in stool samples provides a non-invasive way to assess the degree of inflammation in the digestive tract. Its detection indicates an active immune response, offering insight into the health of the intestinal lining.
Infections That Elevate Calprotectin
Various types of infections can trigger an inflammatory response in the intestines, leading to elevated calprotectin levels. Bacterial infections are a common cause, often resulting in significant increases. Pathogens such as Clostridioides difficile (C. diff), Salmonella, Shigella, and Campylobacter can invade the intestinal lining, causing direct damage and a robust immune reaction. Certain E. coli strains also contribute to this inflammatory state, prompting a substantial release of calprotectin.
Viral infections, while typically causing less severe inflammation than bacterial ones, can also elevate calprotectin. Viruses like Norovirus and Rotavirus cause acute gastroenteritis, leading to intestinal irritation and an immune response. Although calprotectin levels in viral cases are generally lower than in bacterial infections, they can still be elevated. This elevation reflects the body’s effort to clear the viral pathogens.
Parasitic infections represent another category of pathogens that can lead to increased calprotectin. Organisms like Giardia lamblia and Cryptosporidium can colonize the intestines and induce an inflammatory reaction. Entamoeba histolytica, which causes amoebic dysentery, can also result in elevated calprotectin. The degree of calprotectin elevation in parasitic infections can vary, with persistent or severe infestations potentially leading to more pronounced increases.
Other Factors That Elevate Calprotectin
While infections are a notable cause, elevated calprotectin is not exclusive to them, as many other conditions can also induce intestinal inflammation. Inflammatory Bowel Disease (IBD), encompassing Crohn’s disease and ulcerative colitis, stands as a primary non-infectious cause. In IBD, chronic inflammation of the digestive tract leads to consistently high calprotectin levels, often making it a diagnostic and monitoring tool for these conditions.
Non-steroidal anti-inflammatory drugs (NSAIDs) can irritate the gut lining and cause inflammation, resulting in elevated calprotectin. Diverticulitis, a condition involving inflammation of small pouches in the digestive tract, is another factor that can increase calprotectin levels. Celiac disease, an autoimmune disorder triggered by gluten, can also cause intestinal inflammation and elevated calprotectin.
Other causes include microscopic colitis, characterized by microscopic inflammation of the colon, and colorectal cancer, which can induce a local inflammatory response. Systemic inflammatory conditions affecting other parts of the body can sometimes lead to mild calprotectin elevations. Factors such as intense physical exercise or obesity can also influence calprotectin levels.
Interpreting Elevated Calprotectin Results
An elevated calprotectin result indicates that inflammation is present in the intestines, but it does not specify the exact cause or location of this inflammation. Normal calprotectin levels are typically below 50 micrograms per gram (µg/g) of stool, though some laboratory kits may consider up to 100 µg/g as normal. Levels exceeding 100-250 µg/g generally suggest active inflammation, with very high levels, often above 250 µg/g or 500-600 µg/g, strongly correlating with significant inflammatory conditions.
Given that multiple factors, including various infections and non-infectious conditions, can cause elevated calprotectin, a high result necessitates further medical evaluation. A healthcare professional will consider the patient’s symptoms, medical history, and other diagnostic tests to pinpoint the specific underlying cause. This diagnostic process may involve additional stool tests, such as cultures to identify bacterial or parasitic pathogens, or more invasive procedures like endoscopy or colonoscopy to directly visualize the intestinal lining. The appropriate treatment will then be determined based on the confirmed diagnosis.