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HelpTest Code CDGF Celiac Disease Gluten-Free Cascade, Serum and Whole Blood
Reporting Name
Celiac Disease Gluten-Free CascadePerforming Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Evaluating patients suspected of having celiac disease who are currently (or were recently) on a gluten-free diet
Method Name
Polymerase Chain Reaction (PCR)/Sequence-Specific Oligonucleotide Probe (SSO)
Ordering Guidance
This cascade should not be used in patients for whom human leukocyte antigen (HLA) DQ2/DQ8 typing has already been performed. For individuals who are positive for either DQ2 and/or DQ8, CDSP / Celiac Disease Serology Cascade, Serum should be ordered to assess for the presence of autoantibodies associated with celiac disease. For individuals who are negative for DQ2 and DQ8, no further testing is necessary as a diagnosis of celiac disease is unlikely.
Cascade testing is recommended 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.
-CDCOM / Celiac Disease Comprehensive Cascade, Serum and Whole Blood: Complete testing including HLA DQ
-CDSP / Celiac Disease Serology Cascade, Serum: Complete serology testing excluding HLA DQ
-CDGF / Celiac Disease Gluten-Free Cascade, Serum and Whole Blood: For patients already adhering to a gluten-free diet
To order individual tests, see Celiac Disease Diagnostic Testing Algorithm
Specimen Required
Both whole blood and serum are required.
Specimen Type: Whole Blood
Container/Tube: Yellow top (ACD solution A or B)
Specimen Volume: 6 mL
Collection Instructions: Send whole blood in original tube. Do not aliquot.
Specimen Type: Serum
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 2 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial
Specimen Type
SerumWhole Blood ACD-B
Specimen Minimum Volume
Blood: 3 mL
Serum: 1.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 21 days | |
| Frozen | 21 days | ||
| Whole Blood ACD-B | Refrigerated (preferred) | ||
| Ambient | |||
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | OK |
Reference Values
HLA-DQ TYPING
Presence of HLA-DQ2 or HLA-DQ8 alleles associated with celiac disease
Interpretation
HLA-DQ Typing:
Approximately 90% to 95% of patients with celiac disease have the HLA-DQ2 allele; most of the remaining patients with celiac disease have the HLA-DQ8 allele. Individuals who do not carry either of these alleles are unlikely to have celiac disease. For these individuals, no further serologic testing is required. However, individuals with these alleles may not, during their lifetime, develop celiac disease. Therefore, the presence of DQ2 or DQ8 does not conclusively establish a diagnosis of celiac disease. For individuals with DQ2 and/or DQ8 alleles, in the context of positive serology and compatible clinical symptoms, small intestinal biopsy is recommended.
Immunoglobulin A:
Total IgA levels below the age-specific reference range suggest either a selective IgA deficiency or a more generalized immunodeficiency. For individuals with a low or high IgA level, additional clinical and laboratory evaluation is recommended. Some individuals may have a partial IgA deficiency in which the IgA levels are detectable but fall below the age-adjusted reference range. For these individuals, both IgA and IgG isotypes for tissue transglutaminase (tTG) and deamidated gliadin antibodies are recommended for the evaluation of celiac disease.
tTG IgA/IgG Antibodies:
Individuals positive for tTG antibodies of the IgA and/or IgG isotype may have celiac disease, and a small intestinal biopsy is recommended. For individuals with selective IgA deficiency, testing for tTG antibodies of the IgG isotype is indicated. In these individuals, a positive tTg IgG antibody result suggests a diagnosis of celiac disease. However, just as with the tTG IgA antibody, a biopsy should be performed to confirm the diagnosis. Negative tTG IgA and/or IgG antibody serology does not exclude a diagnosis of celiac disease, as antibody levels decrease over time in patients who have been following a gluten-free diet.
Deamidated Gliadin IgA/IgG Antibodies:
Positivity for deamidated gliadin antibodies of the IgA and/or IgG isotype is suggestive of celiac disease, and a small intestinal biopsy is recommended. For individuals with selective IgA deficiency, testing for deamidated gliadin antibodies of the IgG isotype is indicated. In these individuals, a positive deamidated gliadin IgG antibody result suggests a diagnosis of celiac disease. However, just as with the deamidated gliadin IgA antibody, a biopsy should be performed to confirm the diagnosis. Negative deamidated gliadin IgA and/or IgG antibody serology does not exclude a diagnosis of celiac disease, as antibody levels decrease over time in patients who have been following a gluten-free diet.
Day(s) Performed
Profile tests: Monday through Friday; Reflex tests: Monday through Saturday
Report Available
9 to 11 daysTest Classification
See Individual Test IDsCPT Code Information
81376 x 2
82784 (if appropriate)
86258 (if appropriate)
86364 (if appropriate)
86231 (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| CDGF | Celiac Disease Gluten-Free Cascade | 94493-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| DQA | DQ alpha 1 | 94495-9 |
| 28991 | Celiac Disease Interpretation | 69048-7 |
| DQB | DQ beta 1 | 53938-7 |
| CELIG | Celiac gene pairs present? | 48767-8 |
Forms
If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Test Request (T728) with the specimen
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CELI2 | HLA-DQ Typing | Yes, (Order CELI) | Yes |
| CDGF1 | Celiac Disease Interpretation | No | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| TTGA | Tissue Transglutaminase Ab, IgA, S | Yes | No |
| DAGL | Gliadin(Deamidated) Ab, IgA, S | Yes | No |
| DGGL | Gliadin(Deamidated) Ab, IgG, S | Yes | No |
| TTGG | Tissue Transglutaminase Ab, IgG, S | Yes | No |
| IGA | Immunoglobulin A (IgA), S | Yes | No |
Testing Algorithm
If HLA-DQ typing is positive or equivocal for DQ2 or DQ8, then IgA, tissue transglutaminase IgA and IgG, and deamidated gliadin IgA and IgG antibody testing will be performed at an additional charge.
The following algorithms are available: