In a patient with left lower quadrant abdominal pain, alternating constipation and diarrhea, and bloating, will fecal calprotectin and fecal lactoferrin help identify celiac disease?

Fecal Calprotectin and Lactoferrin Are NOT Reliable for Diagnosing Celiac Disease

No, fecal calprotectin and lactoferrin should not be used to identify celiac disease in your patient with left lower quadrant pain, alternating bowel habits, and bloating. The established diagnostic pathway for celiac disease relies on serology (IgA anti-tissue transglutaminase antibody) followed by upper endoscopy with duodenal biopsies, not fecal markers 1.

Why Fecal Markers Are Inadequate

The Guideline-Based Approach

The ACG guidelines are explicit: diagnosis should be based on IgA anti-TTG antibody testing (the preferred test), followed by confirmatory upper endoscopy with histologic analysis of multiple duodenal biopsies 1. Fecal markers are conspicuously absent from this diagnostic algorithm because they lack the sensitivity and specificity needed for celiac disease detection.

The Evidence Against Fecal Markers

Fecal calprotectin has poor sensitivity for celiac disease:

• A 2003 study showed that celiac disease was the primary cause of false-negative results when using fecal calprotectin to distinguish organic causes of chronic diarrhea from IBS 2
• The most recent 2025 study definitively concluded that fecal calprotectin is unreliable for monitoring mucosal healing in celiac disease, showing no correlation with histological remission or lesion grades 3
• While a 2012 pediatric study found elevated calprotectin in untreated celiac disease 4, this finding has limited clinical utility since it doesn't help establish the diagnosis initially

Fecal lactoferrin shows marginal utility:

• A 2023 study found that while fecal lipocalin-2 was elevated in celiac disease, fecal alpha-1-antitrypsin (a protein loss marker similar to lactoferrin) was not significantly different between celiac patients and controls 5
• When alpha-1-antitrypsin was >100mg/dL, it was 90% specific but poorly sensitive for celiac disease 5

The Correct Diagnostic Algorithm for Your Patient

1. Order IgA anti-TTG antibody as the first-line test 1
2. Measure total IgA level simultaneously to rule out IgA deficiency (which would cause false-negative TTG results) 1
3. If IgA deficient, use IgG-based testing (IgG-TTG or IgG-deamidated gliadin peptides) 1
4. If serology is positive, proceed to upper endoscopy with multiple duodenal biopsies for histologic confirmation 1
5. Ensure the patient remains on a gluten-containing diet throughout testing, as a gluten-free diet will cause false-negative results 1

Important Caveats

• Your patient's symptoms (left lower quadrant pain, alternating bowel habits, bloating) overlap significantly with IBS, which has modest celiac disease prevalence 1
• Fecal calprotectin is excellent for identifying inflammatory bowel disease (100% sensitivity in adults 2), but this is a different clinical question
• The 2025 data showing fecal calprotectin correlates with severe disease phenotypes in celiac disease 6 is irrelevant for initial diagnosis—it only applies to monitoring established complicated cases

Bottom line: Use serology (IgA anti-TTG) and endoscopic biopsy, not fecal markers, to diagnose celiac disease 1.