When inflammation occurs in a child’s digestive tract, the body sends immune cells, specifically neutrophils, to the site of irritation. Calprotectin is a protein highly abundant within these neutrophils. When neutrophils are activated and move into the gut lining, they release this protein into the intestinal contents. The fecal calprotectin test measures the amount of this protein in a stool sample, providing an indirect measure of intestinal inflammation. A high result indicates an active inflammatory process somewhere in the gastrointestinal system, though the test does not specify the exact cause.
Understanding the Fecal Calprotectin Test
The fecal calprotectin test is widely used in pediatrics to distinguish between inflammatory conditions and non-inflammatory issues, such as functional gastrointestinal disorders. It is considered a biomarker because its concentration is directly proportional to the number of neutrophils recruited to the gut lining. Interpreting the result requires considering the child’s age, as baseline levels are naturally higher in infants and decrease as the child gets older.
For children four years of age and older, a result below 50 micrograms per gram (\(\mu\)g/g) is considered normal, suggesting active inflammation is unlikely. Results between 50 to 120 \(\mu\)g/g are often classified as borderline or mildly elevated. These lower elevations may suggest a mild inflammatory process or a non-chronic issue.
A result significantly higher than 120 \(\mu\)g/g, and especially above 250 \(\mu\)g/g, suggests an active inflammatory process. The test is a marker of inflammation, not a definitive diagnosis. Determining the underlying cause requires assessing the overall clinical picture, including the child’s symptoms and other test results.
Chronic Inflammatory Bowel Disease
The most significant concern associated with persistently high fecal calprotectin levels in children is chronic Inflammatory Bowel Disease (IBD). IBD covers Crohn’s Disease and Ulcerative Colitis, both involving chronic inflammation of the gastrointestinal tract. Calprotectin is a sensitive tool for IBD because the disease causes a continuous recruitment of neutrophils to the gut lining.
In IBD, the immune system mistakenly attacks the digestive tract, leading to persistent injury and a steady release of calprotectin. Elevated levels often correlate with the severity of the disease and the extent of mucosal inflammation. Children with IBD typically have substantially elevated levels, often rising into the hundreds or even thousands of micrograms per gram.
Crohn’s disease can affect any part of the digestive tract; Ulcerative Colitis is limited to the large intestine and rectum. Both conditions present with symptoms like persistent diarrhea, blood in the stool, unexplained weight loss, and chronic abdominal pain. A fecal calprotectin result of 600 \(\mu\)g/g or higher, paired with these symptoms, makes an IBD diagnosis more likely.
Temporary and Non-IBD Factors
A high calprotectin result does not automatically confirm IBD, as numerous other conditions can trigger an inflammatory response. Many alternative causes are temporary or represent less severe, non-chronic issues. Acute gastroenteritis, caused by viral, bacterial, or parasitic infections, is a common reason for a sudden spike in calprotectin levels.
These infections cause a temporary but intense influx of neutrophils into the gut lining, leading to a transient elevation. Bacterial infections tend to produce higher calprotectin values than viral ones, and levels often increase with the severity of the diarrhea. Once the infection resolves, the calprotectin level typically drops back down to the normal range.
Certain medications can also irritate the digestive lining and cause inflammation, resulting in a temporary elevation. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as ibuprofen, are known to cause transient gut irritation.
Other Non-IBD Causes
Other conditions that can cause elevated calprotectin include Celiac disease, Cow’s Milk Protein Allergy (CMPA), and gastrointestinal involvement in systemic conditions like Henoch-Schönlein purpura. These non-IBD causes are suspected when the level is elevated but not chronically high, or if the level fluctuates significantly upon repeat testing.
Next Steps After a High Result
Receiving a high calprotectin result requires a structured approach to determine the precise cause of the inflammation. The first step involves a full clinical evaluation by a healthcare provider who will assess the child’s symptoms, medical history, and family history. Since the test is highly sensitive, the provider often suggests repeating the fecal calprotectin test, especially if the initial result was borderline or moderately elevated.
If the calprotectin level remains high or if the child is experiencing persistent alarm symptoms, a referral to a pediatric gastroenterologist is necessary. The specialist uses the calprotectin result alongside other diagnostic tools. These tools include specific blood work to check for systemic inflammation, nutritional deficiencies, and antibodies.
The definitive diagnosis of IBD requires direct visualization and tissue sampling of the intestinal lining, not the calprotectin test alone. This is accomplished through endoscopic procedures, such as a colonoscopy or esophagogastroduodenoscopy (EGD). These invasive tests allow the specialist to collect biopsies for histological analysis, providing the final evidence needed to confirm or rule out chronic inflammatory disease.