What are the indications for stool testing in Inflammatory Bowel Disease (IBD)?

From the Guidelines

Stool testing for inflammatory bowel disease (IBD) should prioritize fecal calprotectin as the primary non-invasive diagnostic tool, with a threshold value of 50 μg/g to optimize sensitivity for IBD. The use of fecal calprotectin is supported by the American Gastroenterological Association (AGA) clinical practice guidelines, which suggest its use to screen for IBD in patients presenting with chronic diarrhea 1. This guideline recommends a threshold value of 50 mg/g for fecal calprotectin to optimize sensitivity for IBD, with a pooled sensitivity of 0.81 and a pooled specificity of 0.87.

Key Points to Consider

• Fecal calprotectin is a sensitive and specific marker of intestinal inflammation, useful in differentiating IBD from irritable bowel syndrome (IBS) 1.
• A normal level of fecal calprotectin has a high negative predictive value for IBD, while a level above 50 μg/g suggests inflammation, and levels exceeding 250 μg/g strongly indicate active IBD.
• Other stool tests, such as fecal lactoferrin and stool cultures, can be helpful in ruling out infectious causes that may mimic IBD symptoms.
• Stool tests should complement, not replace, endoscopy with biopsy, which remains the gold standard for IBD diagnosis.
• Regular fecal calprotectin monitoring can help assess treatment response and predict relapse, potentially reducing the need for repeated invasive procedures 1.

Clinical Context and Interpretation

• Fecal calprotectin results must be interpreted in clinical context, considering factors such as clinical symptoms, blood markers like CRP and ESR, and imaging studies.
• False positives can occur with infections, certain medications like NSAIDs, and in older adults, so results must be carefully evaluated.
• The British Society of Gastroenterology consensus guidelines recommend using a higher threshold of fecal calprotectin (between 100 and 250 μg/g) to trigger colonoscopy, improving the positive predictive value with little reduction in the negative predictive value 1.

From the Research

Stool Testing for IBD

• Stool testing, particularly fecal calprotectin, has been found to be a useful tool in distinguishing between inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) 2, 3, 4.
• Fecal calprotectin is a biomarker of gastrointestinal inflammation and has been studied extensively in the diagnosis and monitoring of IBD 3, 5, 6.
• The test can help identify patients with IBD who are in remission but have coexisting IBS-like symptoms, allowing for intensified follow-up and treatment 2.
• Fecal calprotectin levels are elevated in patients with IBD, particularly those with Crohn's disease and ulcerative colitis, and can be used to assess disease activity and response to treatment 3, 5, 6.
• The use of fecal calprotectin testing has several advantages, including being non-invasive, easy to perform, and relatively inexpensive, making it a valuable tool in the diagnosis and management of IBD 5, 6.

Diagnostic Value of Fecal Calprotectin

• Fecal calprotectin has been shown to be a reliable marker for intestinal inflammation and can be used to differentiate between IBD and IBS 4.
• The test has good performance in discriminating between functional and organic bowel processes, allowing for accurate diagnosis and monitoring of IBD 6.
• Fecal calprotectin levels can also be used to evaluate the degree of disease activity and monitor therapeutic response in patients with IBD 6.

Clinical Applications

• Fecal calprotectin testing can be used in clinical practice to aid in the diagnosis of IBD, particularly in patients with unclear or overlapping symptoms with IBS 2, 3, 4.
• The test can also be used to monitor disease activity and response to treatment, allowing for adjustments to be made to treatment plans as needed 3, 5, 6.