What is the most appropriate method to ascertain poor compliance with a gluten-free diet in a patient with celiac disease?

Most Appropriate Method to Ascertain Poor Gluten-Free Diet Compliance

A food diary (standardized adherence questionnaire) is the most appropriate initial method to assess gluten-free diet compliance in this patient with suspected poor adherence, as it provides superior assessment compared to simple self-report and is more practical than invasive testing or serology alone. 1

Rationale for Standardized Dietary Assessment

The 2024 Nature Reviews Gastroenterology & Hepatology guidelines provide clear direction on this clinical scenario:

• Standardized patient-reported adherence questionnaires (such as the Celiac Dietary Adherence Test or Biagi score) are superior to simple patient self-reports and should be used when expert dietician assessment is not readily available 1

• These questionnaires are specifically recommended as part of a holistic clinical assessment for patients with ongoing symptoms and suspected non-responsive celiac disease 1

• The most commonly validated tools include the CDAT (higher sensitivity) and Biagi score (higher specificity), both with similar overall operating characteristics 1

Why Not the Other Options?

Tissue Transglutaminase Antibodies (Option D)

While routinely recommended for monitoring, serology has poor sensitivity (52-57%) for detecting dietary transgressions 1:

• Positive anti-TG2 IgA strongly suggests poor adherence or gluten contamination 1
• However, negative serology cannot confirm strict adherence or lack of gluten exposure 1
• Many patients with ongoing gluten consumption remain seronegative 1

Anti-Endomysial Antibodies (Option C)

• Performs similarly to anti-TG2 IgA with a tendency toward higher specificity but still inadequate sensitivity 1
• Not superior to tissue transglutaminase testing for this purpose 1

Duodenal Biopsy (Option B)

• Routine re-biopsy is NOT recommended in patients with celiac disease on a gluten-free diet 1
• Reserved for cases where non-responsive disease persists despite comprehensive assessment 1
• Invasive, expensive, and not first-line for adherence assessment 1

Optimal Clinical Approach

The algorithmic approach should be:

1. First-line: Administer a standardized adherence questionnaire (CDAT or Biagi score) 1

   • Can be completed quickly and provides structured assessment 2, 3
   • Superior to unstructured dietary history 1

2. Concurrent: Check anti-TG2 IgA serology 1

   • If positive, strongly suggests gluten exposure 1
   • If negative, does NOT rule out non-adherence 1

3. Ideally: Refer to expert dietician for comprehensive dietary evaluation 1

   • This remains the gold standard but may not be readily available 1
   • Standardized Dietician Evaluation (SDE) performs better than questionnaires and serology 1, 4

4. If non-responsive disease persists: Consider urinary/stool gluten immunogenic peptides (GIPs) 1

   • Strong recommendation for cases of suspected ongoing gluten intake 1
   • The only direct method to detect actual gluten consumption 1
   • Detects 97-100% of unrestricted gluten intake 1

Common Pitfalls

• Do not rely on serology alone to assess adherence—it has poor negative predictive value 1
• Do not proceed directly to repeat biopsy without comprehensive dietary assessment first 1
• Remember that ongoing symptoms have multiple potential causes beyond gluten exposure, including small intestinal bacterial overgrowth, microscopic colitis, or refractory celiac disease 1
• Cross-contamination is a major cause of inadvertent non-adherence, even in motivated patients 5

Answer: A. Food diary (specifically, a standardized adherence questionnaire such as CDAT or Biagi score)