Calprotectin is a protein released by specific white blood cells, known as neutrophils, when inflammation is present in the body, particularly within the gut. This protein serves as a marker that can be measured in stool samples to assess the presence and extent of intestinal inflammation. It provides a non-invasive way to gain insight into the state of the digestive tract.
What is Calprotectin and Why is it Tested?
Calprotectin acts as a biomarker, indicating inflammation specifically within the gastrointestinal system. It is primarily utilized to help differentiate between inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, and non-inflammatory conditions like irritable bowel syndrome (IBS). While symptoms of IBD and IBS can overlap, IBD involves actual inflammation, whereas IBS does not.
The test helps medical professionals avoid unnecessary invasive procedures, like colonoscopies, when significant inflammation is unlikely. A calprotectin test is a cost-effective tool that aids in determining the next steps for diagnosis and managing bowel conditions. It helps to build a picture of what might be causing symptoms, though it indicates inflammation generally and not a specific disease.
Understanding Calprotectin Levels by Age
The normal range for calprotectin levels can differ significantly across various age groups, with infants and young children having higher values than adolescents and adults. This variation is largely attributed to factors such as gut maturation and different immune responses in early life.
In infants aged 1 to 3 months, median calprotectin levels can be around 375.2 µg/g, dropping to approximately 217.9 µg/g for those aged 3 to 6 months. Levels continue to decrease as children grow older, with medians around 127.7 µg/g for 6 to 9 months, 96.1 µg/g for 9 to 12 months, and 104.2 µg/g for 12 to 18 months.
For children aged 1 to 4 years, median calprotectin concentrations may be around 75 µg/g, further decreasing to about 28 µg/g for children aged 4 to 12 years. In contrast, adults have normal calprotectin values below 50 µg/g. Some studies suggest age-related reference ranges for adults, indicating that levels can rise with age, with an average of 15.88 µg/g for those under 50 years, 35.46 µg/g for ages 50-69 years, and up to 160.3 µg/g for individuals over 70 years.
Interpreting Calprotectin Test Results
Calprotectin test results provide a general indication of intestinal inflammation, but they do not diagnose a specific disease. Levels within the normal range, typically below 50 µg/g for adults, suggest no significant intestinal inflammation, making inflammatory conditions like IBD unlikely. This can help rule out IBD in undiagnosed patients experiencing gastrointestinal symptoms.
Levels above the normal range indicate the presence of inflammation, with higher concentrations correlating with more severe inflammation. For instance, levels between 50 and 120 µg/g are considered borderline elevated, and a repeat test may be recommended. Levels greater than 120 µg/g suggest significant inflammation, while levels exceeding 250 µg/g are often associated with active inflammatory bowel disease. These results must always be interpreted by a healthcare professional in conjunction with a patient’s symptoms and other clinical findings.
Factors Influencing Calprotectin Levels
Several factors beyond chronic inflammatory bowel disease can influence calprotectin levels, leading to elevated results. Acute gastrointestinal infections, whether bacterial, viral, or parasitic, can cause a temporary rise in calprotectin due to the body’s inflammatory response. Bacterial infections tend to cause more significant increases compared to viral infections.
Certain medications, such as non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen, can also elevate calprotectin levels by causing irritation in the intestines. Other conditions, including colorectal cancer, polyps, microscopic colitis, diverticulitis, and celiac disease, may also lead to increased calprotectin levels.