Calprotectin • Chronic Diarrhea Workup
Enter the faecal calprotectin level to visualize clinical status.
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Differentiating between Inflammatory Bowel Disease (IBD) and Irritable Bowel Syndrome (IBS)
Monitoring disease activity and therapeutic response in Ulcerative Colitis and Crohn's disease
Predicting clinical relapse in patients with known IBD in steroid-free remission
To guide decision-making for colonoscopy referral in primary care
Biological Mechanism
Calprotectin is a calcium-binding protein complex found predominantly in neutrophilic granulocytes. Its presence in stool is a direct surrogate marker for neutrophilic migration into the gut lumen, indicating mucosal inflammation.
How it Works
The Diagnostic Thresholds
| < 50 μg/g | Normal / Non-inflammatory. Suggests IBS/Functional disease. |
| 50–150 μg/g | Indeterminate / Mildly abnormal. Consider NSAID use or infection. |
| > 150 μg/g | Abnormal. High suspicion for IBD or active mucosal injury. |
| > 250 μg/g | Highly Active IBD / Relapse risk. |
Relapse Prediction
01
Two consecutive readings > 150–200 μg/g in a patient with quiescent IBD predict clinical relapse within 3–6 months with a sensitivity of ~80%.
Confounding Factors (False Positives)
Regular NSAID use (can cause "NSAID Colopathy" and mild elevations)
Infectious Gastroenteritis (Bacterial/Viral)
Proton Pump Inhibitors (PPIs) — some studies suggest mild non-specific increases
Very young age (infants naturally have higher calprotectin levels)
Clinical Pearls
Calprotectin vs. CRP
C-Reactive Protein (CRP) is a systemic marker of inflammation. Fecal Calprotectin is a local marker. Calprotectin is significantly more sensitive than CRP for detecting low-grade mucosal inflammation, particularly in restricted Crohn's disease or Ulcerative Proctitis.
Optimizing Colonoscopy
Using a calprotectin threshold of 50–100 μg/g in primary care can reduce the number of "unnecessary" colonoscopies in young patients with abdominal pain/bloating by up to 67%, while rarely missing an IBD diagnosis.
Clinical Pearls
Wait at least 2 weeks after an episode of acute infective diarrhea or stopping NSAIDs before testing calprotectin
Levels > 250 μg/g in UC patients are strongly correlated with endoscopic Mayo Grade 2-3
Consistent "Low" calprotectin (< 50) is the cornerstone of "Treat-to-target" monitoring to ensure biological maintenance
Next Steps
Action Pathways
01
Level < 50: Reassure; investigate for IBS (FODMAP trial, etc.).
02
Level 50–150: Repeat in 4 weeks. Exclude NSAID use.
03
Level > 150: Refer to Gastroenterology; prioritize for colonoscopy staging.
Complementary Lab Tools
C-Reactive Protein (CRP) Interpretation
Fecal Lactoferrin
IBD-U (Unclassified) Serology
The Evidence
NICE Guidelines (UK)
Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel.
NICE. • NICE Diagnostics Guidance [DG11]. 2013;Establishing the standard use of calprotectin in primary care triage.
View Source• . ;
Meta-analysis of Diagnostic Accuracy
Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis.
Van Rheenen PF et al. • BMJ. 2010;341:c3369. Large scale analysis showing NPV of calprotectin for IBD.
View SourceOrigins & History
The S100 Protein Family
Calprotectin was first discovered as "the L1 protein" by Fagerhol in the 1980s. Its application to stool samples in the 1990s was a breakthrough in non-invasive monitoring. It is now part of the WHO List of Essential In Vitro Diagnostics.
Last Comprehensive Review: 2026-07-17