What are the steps for testing and treating celiac disease?

Testing and Treatment for Celiac Disease

The diagnostic approach for celiac disease begins with IgA tissue transglutaminase antibody (tTG-IgA) testing while the patient is on a gluten-containing diet, followed by intestinal biopsy for confirmation, and treatment consists of a strict lifelong gluten-free diet. 1

Diagnostic Testing Algorithm

Initial Serologic Testing

• tTG-IgA is the primary screening test with high sensitivity (90-96%) and specificity (>95%) 1
• Total IgA levels should be measured to rule out IgA deficiency 2, 1
• Testing must be performed while the patient is on a gluten-containing diet (at least 10g daily for 6-8 weeks) 1, 3
• In patients with high tTG-IgA levels (>10x upper limit of normal), IgA endomysial antibody (EMA-IgA) should be performed as a confirmatory test with excellent specificity (99.6%) 2, 1

Confirmatory Testing

• Intestinal biopsy remains the gold standard for diagnosis in adults 2, 1
• Multiple biopsy specimens (ideally 6) should be taken from the second part of the duodenum or beyond 1, 4
• Characteristic histologic findings include villous atrophy, crypt lengthening, and increased intraepithelial lymphocytes 1
• In adults with tTG-IgA >10x upper limit of normal plus positive EMA-IgA, the positive predictive value for celiac disease approaches 100%, though biopsy may still be performed for differential diagnosis 2

Special Testing Considerations

• In IgA-deficient patients, IgG-based tests should be used (IgG deamidated gliadin peptide or IgG tTG) 2, 1
• HLA-DQ2 and HLA-DQ8 testing has high negative predictive value and is useful when celiac disease is strongly suspected despite negative serology 1, 4
• In children with tTG-IgA ≥10× upper limit of normal, positive EMA-IgA, and positive HLA, biopsy may be avoided according to recent guidelines 1

Treatment Approach

Gluten-Free Diet

• Strict lifelong gluten-free diet is the only effective treatment for celiac disease 5
• Patients should be referred to a dietitian experienced in celiac disease management 4
• The diet requires elimination of wheat, rye, and barley 5

Monitoring Response to Treatment

• Follow-up serology should be performed at 6 and 12 months after diagnosis, and yearly thereafter 2
• Negative serology after treatment does not guarantee intestinal mucosal healing 2, 6
• Persistently positive serology usually indicates ongoing intestinal damage and continued gluten exposure 2
• Patients with persistent or relapsing symptoms should undergo repeat endoscopic biopsies to determine healing, even with negative tTG-IgA 2

High-Risk Groups to Consider Testing

• First-degree relatives of patients with celiac disease 1, 3
• Patients with type 1 diabetes mellitus 1, 7
• Patients with unexplained iron deficiency anemia 1, 3
• Patients with premature osteoporosis 1, 3
• Patients with autoimmune thyroid disease 1, 3
• Patients with unexplained liver transaminase elevations 1
• Patients with Down syndrome 1

Common Pitfalls in Diagnosis and Management

• Initiating a gluten-free diet before completing diagnostic testing can lead to false-negative results 4, 3
• Relying solely on serology without biopsy confirmation can lead to misdiagnosis 4, 3
• IgG isotype testing for tTG antibody is not specific in the absence of IgA deficiency 2
• Seronegative celiac disease can occur and requires biopsy for diagnosis 3
• Patients who have already started a gluten-free diet prior to diagnosis should resume a normal diet with three slices of wheat bread daily for 1-3 months before repeat testing 2

By following this systematic approach to testing and treatment, celiac disease can be accurately diagnosed and effectively managed to prevent complications and improve quality of life.