What is the significance of a fecal calprotectin level of 128 ug/g and what are the recommended next steps for management?

Management of Fecal Calprotectin 128 μg/g

A fecal calprotectin level of 128 μg/g falls into the intermediate range (100-250 μg/g) and requires either repeat testing or gastroenterology referral based on symptom severity and clinical suspicion for IBD. 1

Immediate Clinical Assessment

Your next steps depend critically on the patient's symptom severity:

For Patients with Moderate-to-Severe Symptoms

Refer urgently to gastroenterology for colonoscopy if the patient has any of the following: 2, 1

• Rectal bleeding with abdominal pain
• Significant weight loss
• Frequent diarrhea (>6 stools daily)
• Nocturnal symptoms
• Iron deficiency anemia

At this calprotectin level (128 μg/g) combined with moderate-to-severe symptoms, the likelihood of endoscopic inflammation is substantial enough to warrant direct endoscopic evaluation rather than repeat testing. 1, 3

For Patients with Mild or Minimal Symptoms

Consider repeat calprotectin testing in 2-3 weeks if symptoms are mild and more consistent with irritable bowel syndrome. 1 The intermediate range has moderate specificity (66%) for detecting active endoscopic inflammation, meaning transient elevations can occur. 1

If repeat testing shows:

• <100 μg/g: Treat as IBS in primary care 2, 1
• Persistently 100-250 μg/g: Refer to gastroenterology for routine evaluation 2, 1
• >250 μg/g: Refer urgently to gastroenterology 2

Essential Baseline Laboratory Testing

Complete these tests before or concurrent with gastroenterology referral: 1

• Complete blood count: Assess for anemia (suggesting chronic blood loss) and thrombocytosis (indicating inflammation) 1
• C-reactive protein: Complementary inflammatory marker, though 20% of active Crohn's patients may have normal CRP 1
• Urea and electrolytes: Evaluate for dehydration and electrolyte abnormalities 1
• Coeliac screen (tissue transglutaminase antibodies): Exclude celiac disease as alternative diagnosis 2, 1
• Stool culture: Exclude infectious causes of inflammation 2, 1

Critical Caveats That Affect Interpretation

NSAID Use

If the patient has used NSAIDs within the past 6 weeks, repeat calprotectin testing after NSAID cessation rather than proceeding directly to colonoscopy. 2, 1 NSAIDs can falsely elevate calprotectin levels, making interpretation unreliable. 2

Other Causes of Elevation

Calprotectin at 128 μg/g is not specific for IBD and can be elevated in: 1, 4

• Infectious gastroenteritis
• Colorectal cancer
• Microscopic colitis
• Hemorrhoids (due to local bleeding and inflammation)

Assay Methodology Matters

The laboratory report indicates results are 40% lower with the specific methodology used compared to the more common Buhlmann assay. For monitoring established IBD with this assay, adjusted thresholds are <60 μg/g for remission and >150 μg/g for relapse. However, for initial diagnosis in a new patient, the standard thresholds (100-250 μg/g intermediate range) still apply. 2

Clinical Context Interpretation

Interpret calprotectin in light of pre-test probability of IBD based on: 2, 1

• Age (16-40 years has higher IBD likelihood)
• Family history of IBD
• Duration of symptoms (>4 weeks)
• Specific symptom pattern (nocturnal diarrhea, blood mixed with stool rather than on surface)

If there is particularly strong clinical suspicion for IBD (family history, classic symptoms, young age), proceed directly to gastroenterology referral even in this intermediate range rather than repeat testing. 2

Alarm Features Requiring Immediate Action

Refer via suspected cancer pathway regardless of calprotectin level if: 2, 1

• Abdominal, rectal, or anal mass
• Unexplained anal ulceration
• Age >40 with new-onset symptoms
• Rectal bleeding with change in bowel habit and weight loss

What Gastroenterology Will Do

Ileocolonoscopy with biopsies is the gold standard for diagnosing IBD, assessing disease extent and severity, and differentiating Crohn's disease from ulcerative colitis. 1 Cross-sectional imaging (MRI or CT enterography) may be needed to assess small bowel involvement and complications. 1

Common Pitfall to Avoid

Do not empirically escalate IBD treatment based on calprotectin alone without endoscopic confirmation in patients with mild symptoms and intermediate calprotectin levels. 1 The American Gastroenterological Association specifically recommends endoscopic assessment rather than empiric treatment adjustment for patients with mild symptoms and elevated calprotectin. 1