What is the recommended clinical blood test for diagnosing celiac disease?

Recommended Blood Test for Celiac Disease Diagnosis

The primary recommended blood test for diagnosing celiac disease is the IgA tissue transglutaminase antibody (tTG-IgA) test, which should be performed while the patient is on a gluten-containing diet. 1

Diagnostic Algorithm for Celiac Disease

1. First-line serological testing:

   • IgA tissue transglutaminase antibody (tTG-IgA)
   • Total serum IgA level (to rule out IgA deficiency)

2. For patients with IgA deficiency (2-3% of celiac patients):

   • IgG-tTG or
   • IgG deaminated gliadin peptides (DGP) testing 1

3. Confirmatory testing for positive tTG-IgA results:

   • IgA endomysial antibody (EMA-IgA) - serves as a highly specific confirmatory test 1

Test Performance Characteristics

• tTG-IgA: Sensitivity of 97.7% and specificity of 70.2% in children 1
• EMA-IgA: Sensitivity of 94.5% and specificity of 93.8% in children 1

Important Considerations

• Testing timing: Blood tests must be performed while the patient is consuming gluten. If already on a gluten-free diet, a gluten challenge with three slices of wheat bread daily for 1-3 months before testing is necessary 1

• Biopsy remains gold standard: Despite excellent serological tests, intestinal biopsy is still considered the definitive diagnostic method, requiring at least 6 specimens due to the patchy nature of intestinal damage 1

• Commercial lab variability: Be aware that test characteristics may vary significantly between commercial laboratories. One study found sensitivity ranging from 40.0% to 86.4% between different labs 2

• Disease severity affects results: Test sensitivity is significantly higher (90.0%) in patients with total villous atrophy compared to those with partial villous atrophy (42.3%) 2

Tests to Avoid

The following tests should NOT be used for celiac disease diagnosis:

• Stool studies
• Small-bowel follow-through
• Intestinal permeability testing
• D-xylose testing
• Salivary testing
• Skin testing 1

Additional Diagnostic Tools

• HLA-DQ2/DQ8 testing: Has high negative predictive value (>99%) and is useful in:
  • Patients with negative serology but strong clinical suspicion
  • Patients already on gluten-free diet without prior testing
  • Patients with equivocal biopsy results 1

High-Risk Groups for Screening

Consider celiac disease testing in:

• First-degree relatives (7.5% risk)
• Patients with type 1 diabetes
• Autoimmune thyroid disease
• Down syndrome
• Turner syndrome
• Unexplained iron deficiency anemia 1

Remember that a negative serology does not guarantee intestinal healing, and persistently positive serology usually indicates ongoing intestinal damage and gluten exposure. Regular monitoring with anti-TG2 antibodies at 6 months, 12 months, and annually thereafter is recommended for diagnosed patients 1.