What is the role of fecal calprotectin in diagnosing and managing inflammatory bowel disease (IBD)?

Role of Fecal Calprotectin in Diagnosing and Managing Inflammatory Bowel Disease

Fecal calprotectin is a highly valuable biomarker for diagnosing inflammatory bowel disease (IBD) in patients with chronic gastrointestinal symptoms, differentiating it from irritable bowel syndrome (IBS), and monitoring disease activity and treatment response in established IBD patients. 1, 2

Diagnostic Role in Suspected IBD

• Fecal calprotectin has a high negative predictive value for IBD, making it an excellent screening tool for patients aged 16-40 presenting with chronic diarrhea and symptoms that may be consistent with either IBD or IBS 1
• For initial screening in primary care, the following interpretation of fecal calprotectin levels is recommended:
  • <100 μg/g: IBS likely, treat as IBS in primary care 1
  • 100-250 μg/g: Consider repeat testing or routine referral to gastroenterology 1

  • 250 μg/g: Refer urgently to gastroenterology 1

• A calprotectin cut-off of 50 μg/g has the best sensitivity (90.6%) to detect endoscopically active disease, while specificity performs best (78.2%) at levels >100 μg/g 1, 3

Monitoring Disease Activity in Established IBD

• Fecal calprotectin is a useful surrogate marker of inflammatory activity in IBD that correlates well with endoscopic inflammation in both ulcerative colitis and Crohn's disease 1, 2
• When it is unclear if symptoms represent a relapse or other causes (particularly in Crohn's disease), calprotectin is useful to confirm active inflammation and can be a non-invasive alternative to endoscopy or imaging 1
• Among patients with elevated fecal calprotectin levels and known IBD, 66% required escalation of therapy within 12 months compared to only 18% of those with normal calprotectin levels 4
• For monitoring disease activity, the following thresholds are suggested:
  • <50-100 μg/g: Quiescent disease likely, continue current therapy 5, 6
  • 100-250 μg/g: Possible inflammation, further testing (e.g., colonoscopy) may be required 5, 6

  • 250 μg/g: Active inflammation likely, strategies to control inflammation should be initiated 5, 6

Practical Considerations for Sample Collection

• The first stool passed in the morning should be routinely used for sampling 1, 7
• Samples should be stored for no more than 3 days at room temperature before analysis 1, 7
• NSAID use in the past 6 weeks can affect calprotectin levels and should be considered when interpreting results 1, 7

Important Limitations and Caveats

• Fecal calprotectin is not sensitive enough to exclude colorectal cancer, so patients with rectal bleeding, abdominal pain, change in bowel habit, weight loss, or iron-deficiency anemia should be referred via a suspected cancer pathway regardless of calprotectin result 1, 2
• Calprotectin can be elevated in various inflammatory conditions beyond IBD, including infectious gastroenteritis and colorectal cancer 2, 8
• Calprotectin performs better in ulcerative colitis than in Crohn's disease (sensitivity 87.3% vs 82.4%, specificity 77.1% vs 72.1%) 3
• Hemorrhoids can cause false elevations in fecal calprotectin levels due to local bleeding and inflammation 2

Advantages Over Traditional Diagnostic Methods

• Fecal calprotectin is non-invasive, making it preferable to endoscopy for initial screening and routine monitoring 9
• Serial calprotectin monitoring at 3-6 month intervals can facilitate early recognition and treatment of impending disease flares 5, 6
• Fecal calprotectin helps determine whether clinical symptoms in patients with known IBD are caused by disease flares or non-inflammatory complications 9

By incorporating fecal calprotectin testing into the diagnostic and monitoring algorithms for IBD, clinicians can reduce unnecessary invasive procedures, improve disease management, and potentially achieve better long-term outcomes for patients.