Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

disorders including thyroiditis, type I diabetes mellitus, Down syndrome, and IgA deficiency.(1,3) Celiac
disease tends to occur in families; individuals with family members who have celiac disease are at
increased risk of developing the disease. Genetic susceptibility is related to specific HLA markers. More
than 97% of individuals with celiac disease in the United States have DQ2 and/or DQ8 HLA markers
compared to approximately 40% of the general population.(3) A definitive diagnosis of celiac disease
requires a jejunal biopsy demonstrating villous atrophy.(1-3) Given the invasive nature and cost of the
biopsy, serologic tests may be used to identify individuals with a high probability of having celiac disease.
Because no single laboratory test can be relied upon completely to establish a diagnosis of celiac disease,
those individuals with positive laboratory results should be referred for small intestinal biopsy, thereby
decreasing the number of unnecessary invasive procedures. Celiac disease is associated with a variety of
autoantibodies, including endomysial (EMA), tissue transglutaminase (tTG), and deamidated gliadin
antibodies.(4) Although the IgA isotype of these antibodies usually predominates in celiac disease,
individuals may also produce IgG isotypes, particularly if the individual is IgA deficient.(2) The most
sensitive and specific serologic tests are tTG and deamidated gliadin antibodies. Testing for IgA and IgG
antibodies to unmodified gliadin proteins is no longer recommended because of the low sensitivity and
specificity of these tests for celiac disease; however, recent studies have identified specific B-cell epitopes
on the gliadin molecule that, when deamidated by the enzyme tTG, have increased sensitivity and
specificity for celiac disease.(5,6) The tests for deamidated gliadin antibodies, IgA and IgG, replace the
older gliadin antibody tests, which have been discontinued at Mayo Clinic. The sensitivity and specificity
of DGLDN/89031 Gliadin (Deamidated) Antibodies Evaluation, IgG and IgA, Serum for untreated,
biopsy-proven celiac disease were comparable to test TSTGP/83671 Tissue Transglutaminase (tTG)
Antibodies, IgA and IgG Profile, Serum in a study conducted at Mayo Clinic.(5) The treatment for celiac
disease is maintenance of a gluten-free diet.(1-3) In most patients who adhere to this diet, levels of
associated autoantibodies decline and villous atrophy improves. This is typically accompanied by an
improvement in clinical symptoms. For evaluation purposes, all serologic tests ordered for the diagnosis
of celiac disease should be performed while the patient is on a gluten-containing diet. Once a patient has
initiated the gluten-free diet, serologic testing may be repeated to assess the response to treatment. In
some patients, it may take up to 1 year for antibody titers to normalize. Persistently elevated results
suggest poor adherence to the gluten-free diet or the possibility of refractory celiac disease.(1) See Celiac
Disease Diagnostic Testing Algorithm in Special Instructions for the recommended approach to a patient
suspected of celiac disease. An algorithm is available for monitoring the patient's response to treatment,
see Celiac Disease Routine Treatment Monitoring Algorithm in Special Instructions. For your
convenience, we recommend utilizing cascade testing for celiac disease. Cascade testing ensures that
testing proceeds in an algorithmic fashion. The following cascades are available; select the appropriate
one for your specific patient situation. Algorithms for the cascade tests are available in Special
Instructions. -CDCOM/89201 Celiac Disease Comprehensive Cascade: complete testing including HLA
DQ -CDSP/89199 Celiac Disease Serology Cascade: complete testing excluding HLA DQ -CDGF/89200
Celiac Disease Comprehensive Cascade for Patients on a Gluten-Free Diet: for patients already adhering
to a gluten-free diet To order individual tests, see Celiac Disease Diagnostic Testing Algorithm in Special
Instructions.
Useful For: Evaluating patients suspected of having celiac disease; this includes patients with
symptoms compatible with celiac disease, patients with atypical symptoms, and individuals at increased
risk of celiac disease Evaluating the response to treatment with a gluten-free diet
Interpretation: Positive test results for deamidated gliadin antibodies, IgA or IgG, are consistent
with the diagnosis of celiac disease. Negative results indicate a decreased likelihood of celiac disease.
Decreased levels of deamidated gliadin antibodies, IgA or IgG, following treatment with a gluten-free
diet are consistent with adherence to the diet. Persistence of high levels of antibodies following dietary
treatment suggest poor adherence to the diet or the presence of refractory disease. See Celiac Disease
Diagnostic Testing Algorithm in Special Instructions for the recommended approach to a patient
suspected of celiac disease. An algorithm is available for monitoring the patient's response to treatment,
see Celiac Disease Routine Treatment Monitoring Algorithm in Special Instructions.
Reference Values:
Negative: 30.0 U
Current as of January 3, 2013 2:22 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 819