Does a fecal calprotectin level of 180 imply Inflammatory Bowel Disease (IBD)?

Interpreting a Fecal Calprotectin Level of 180 μg/g

A fecal calprotectin level of 180 μg/g falls within the intermediate range (100-250 μg/g) and suggests possible inflammatory bowel disease (IBD) that requires further evaluation, but does not definitively confirm IBD. 1, 2

Diagnostic Significance of Fecal Calprotectin Values

• Fecal calprotectin is a validated biomarker for intestinal inflammation that correlates well with endoscopic and histological disease activity in IBD 1
• Values are interpreted according to established thresholds:
  • <100 μg/g: IBS is more likely than IBD 1
  • 100-250 μg/g (including 180 μg/g): Intermediate range requiring clinical correlation 1, 2

  • 250 μg/g: Strongly suggestive of active IBD requiring urgent gastroenterology referral 1

Clinical Approach to a Value of 180 μg/g

• For patients aged 16-40 with chronic diarrhea and symptoms that may be consistent with either IBD or IBS, a value of 180 μg/g warrants:

  • Exclusion of infectious causes 1
  • Consideration of repeat testing or routine referral to gastroenterology 1
  • Clinical correlation with patient symptoms and risk factors 2

• The British Society of Gastroenterology recommends that interpretation should consider the pre-test probability of IBD 1:

  • With strong clinical suspicion of IBD (based on clinical features or family history), referral to gastroenterology is advised even for intermediate values like 180 μg/g 1
  • With symptoms more suggestive of IBS, repeat testing may be appropriate 1

Diagnostic Performance at Different Thresholds

• A meta-analysis found that a calprotectin cut-off of 50 μg/g had the best sensitivity (90.6%) to detect endoscopically active disease 1
• Specificity performs best (78.2%) at levels >100 μg/g 1
• A threshold of 250 μg/g provides better specificity (82%) compared to 100 μg/g (66%) for differentiating active IBD from remission 1

Important Caveats and Limitations

• False positives can occur with:

  • NSAID use in the past 6 weeks 1, 2
  • Infectious gastroenteritis 2, 3
  • Colorectal cancer 1, 2
  • Other inflammatory conditions 2, 3

• Practical considerations for sample collection:

  • First morning stool is preferred 1
  • Samples should be stored for no more than 3 days at room temperature before analysis 1
  • Variability exists between different assays 1

Next Steps for a Patient with Calprotectin of 180 μg/g

• Rule out infectious causes with stool cultures 1
• Consider other baseline tests: CBC, CRP, electrolytes, coeliac screen 1
• If strong clinical suspicion for IBD exists, refer to gastroenterology 1
• If symptoms are more consistent with IBS but diagnostic uncertainty remains, consider repeat testing 1
• For patients with concerning symptoms (rectal bleeding, weight loss, iron deficiency anemia), consider cancer pathway referral regardless of calprotectin value 1

In summary, a fecal calprotectin of 180 μg/g represents an intermediate value that suggests possible IBD but requires clinical correlation and likely further evaluation to establish a definitive diagnosis 1, 2.