What tests should be ordered for a celiac disease panel?

Celiac Disease Panel: Recommended Tests for Diagnosis

The primary celiac disease panel should include IgA tissue transglutaminase (tTG) antibody as the first-line test, along with total serum IgA measurement to rule out IgA deficiency. 1

Primary Testing Algorithm

First-line Testing:

• IgA tissue transglutaminase (tTG) antibody - The preferred initial test for patients over age 2 1
• Total serum IgA - To rule out IgA deficiency, particularly in high-risk patients 1

For IgA-deficient patients:

• IgG tissue transglutaminase (tTG) or
• IgG deamidated gliadin peptide (DGP) antibodies 1

For weakly positive IgA tTG or high clinical suspicion:

• IgA endomysial antibody (EMA) - Highly specific (>99%) but more labor-intensive 1

Testing Considerations

Important Clinical Notes:

• All serologic testing must be performed while the patient is on a gluten-containing diet (at least 3 slices of wheat bread daily for 1-3 months) 1
• Antibodies against native gliadin are no longer recommended for primary detection 1
• In children under 2 years, combine tTG IgA with IgG/IgA deamidated gliadin peptides for improved sensitivity 1

Diagnostic Thresholds:

• tTG-IgA levels >10x upper limit of normal with positive EMA have nearly 100% positive predictive value for celiac disease 1
• High titer results (>118 U) may allow diagnosis without biopsy in symptomatic adults 2

Confirmatory Testing:

• Upper endoscopy with multiple duodenal biopsies remains the gold standard for diagnosis 1
• Recommended biopsy protocol: 1-2 specimens from duodenal bulb and at least 4 from distal duodenum 1

Special Circumstances

For Equivocal Cases:

• HLA-DQ2/DQ8 testing - Useful in:
  • Patients with equivocal biopsy findings
  • Those already on gluten-free diet without prior testing
  • Cases with discrepant serology and histology
  • When original diagnosis is questioned 1

Pitfalls to Avoid:

1. Do not test patients already on a gluten-free diet - false negatives are common 1
2. Do not rely on serologic tests to monitor mucosal healing - they have poor sensitivity (<50%) for persistent villous atrophy in treated patients 3
3. Do not use stool studies, intestinal permeability tests, or salivary tests - these are not recommended for diagnosis 1
4. Do not use antibodies against native gliadin - these have inferior diagnostic performance 1

The combination of IgA tTG and total IgA provides the most efficient initial testing strategy for celiac disease detection, with appropriate follow-up testing based on results and clinical suspicion. This approach optimizes diagnostic accuracy while minimizing unnecessary testing.