A person seeking diagnosis MUST be following a daily diet that contains gluten for at least 4 weeks in order for test results to be accurate. Specific antibody blood tests are the initial step in screening for CD. Patients should always consult with a physician to ensure proper diagnosis.
Recommended Blood Tests:
- Anti-tissue transglutaminase antibody (tTG – IgA and IgG)
commonly used whether or not symptoms are present and the most sensitive test available
- Anti-endomysial antibody (EMA-IgA) – highly specific marker for celiac disease
- Anti-deaminated gliadin peptide (DGP – IgA and IgG)
used when tTG or EMA is negative and in cases where patient is IgA deficient
- Total serum IgA – used to check levels to exclude selective IgA deficiency that results in a false negative test
- Anti-gliadin antibody (AgA – IgG and IgA) not considered sensitive or specific enough for adults, but used for children under 2 because tTG and EMA antibodies may be absent. The anti-DGP test is sensitive in this group.
A patient with positive antibody tests and a patient with selective IgA deficiency are strongly advised to consult with their physician regarding a small bowel biopsy (which is performed endoscopically). A positive small bowel biopsy is required to confirm the diagnosis and assess the degree of damage to the villi in the intestinal lining. Antibody test results can only suggest the presence of Celiac Disease but cannot confirm it. When antibody results and biopsy are inconclusive, or when the patient is on a gluten-free diet, genetic testing of the HLA (human leukocyte antigen) DQ2/DQ8 genes may be helpful. The specific genes DQ2 and/or DQ8 are considered necessary for Celiac Disease to develop. Since one-third of the population also has these genes, the presence of DQ2 or DQ8 does not imply that the person will necessarily develop CD, rather, that they have a genetic predisposition to CD.
Genetic testing does not diagnose Celiac Disease - its largest benefit is that the absence of DQ2 and DQ8 essentially excludes CD.
The onset of Celiac Disease can occur at any time in a person’s life. Once a person is diagnosed, family members should be urged to get tested as well.