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Test Code LABCEHLA Celiac Associated HLA-DQ Alpha 1 and DQ Beta 1 DNA Typing, Blood

Additional Codes

 

Test Name in EPIC EPIC Test Code Mnemonic Mayo Test ID
CELIAC ASSOCIATED HLA-DQ TYPING LABCEHLA CELI CELI

 

Reporting Name

Celiac Associated HLA-DQ Typing

Useful For

Assessing risk of celiac disease

Method Name

Polymerase Chain Reaction (PCR)/Sequence-Specific Oligonucleotide Probe (SSO)

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood ACD-B


Ordering Guidance


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 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


Container/Tube: Yellow top (ACD Solution A or B)

Specimen Volume: 6 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD-B Refrigerated (preferred)
  Ambient 

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

An interpretive report will be provided.

Day(s) Performed

Monday through Friday

CPT Code Information

81376 x 2-HLA Class II typing, low resolution (eg, antigen equivalents); one locus (eg, HLA-DRB1/3/4/5, -DQB1, -DQA1, -DPB1, or -DPA1), each

 

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CELI Celiac Associated HLA-DQ Typing 94492-6

 

Result ID Test Result Name Result LOINC Value
DQA DQ alpha 1 94495-9
DQB DQ beta 1 53938-7
CELIG Celiac gene pairs present? 48767-8
CELIC Interpretation 69048-7

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

Clinical Information

Celiac disease (gluten-sensitive enteropathy) is mediated by T lymphocytes in patients with genetic susceptibility. This genetic association is with certain HLA genes in the class II region (DQ alpha 1, DQ beta 1).

Interpretation

Most (90%-95%) patients with celiac disease have 1 or 2 copies of HLA-DQ2 haplotype (see below), while the remainder have HLA-DQ8 haplotype. Rare exceptions to these associations have been occasionally seen. In one study of celiac disease, only 0.7% of patients with celiac disease lacked the HLA alleles mentioned above. Results are reported as permissive, nonpermissive, or equivocal gene pairs.

 

It is important to realize that these genes are also present in about 20% of people without celiac disease. Therefore, the mere presence of these genes does not prove the presence of celiac disease or that genetic susceptibility to celiac disease is present.

 

The HLA-DQ molecule is composed of 2 chains: DQ alpha (encoded by HLA-DQA1 gene) and DQ beta (encoded by HLA-DQB1 gene). HLA-DQ typing can be performed by serological or molecular methods. Currently, most laboratories perform typing by molecular methods. HLA-DQ2 and DQ8, as typed by serology, are usually based on the molecular typing of the DQB1 chain only. The current molecular method allows typing for both the DQB1 and DQA1 chains. This has shown that there are different haplotypes of HLA-DQ2 and DQ8. Typing of these haplotypes is important in celiac disease as they carry different risk association.

 

There are 2 common haplotypes of DQ2:

1. DQA1*05:01 with DQB1*02:01, also called DQ2.5 in celiac literature

2. DQA1*02:01 with DQB1*02:02, also called DQ2.2 in celiac literature

A single haplotype (heterozygote) of DQ2.5 is permissive for presence of celiac genes. However, only a double haplotype (homozygous) of DQ2.2 is permissive for presence of celiac genes. There are few reports where a single haplotype of DQ2.2 is considered to be an equivocal risk. In some cases, the DQ2.2 haplotype may be present with a DQ7.5 haplotype (DQA1*05:05 with DQB1*03:01). In this case, a DQ2.5 molecule can be formed by the combination of DQB1*02:02 from one chromosome and DQA1*05:05 from the other chromosome. These cases fall in the same category as the DQ2.5 heterozygote.

 

There are 3 common haplotypes of DQ8:

1. DQA1*03:01 with DQB1*03:02

2. DQA1*03:02 with DQB1*03:02

3. DQA1*03:03 with DQB1*03:02

Any single haplotype (heterozygote) of DQ8 is permissive for celiac.

 

Therefore, the gene pairs permissive for celiac are:

1. Heterozygote (single copy)

-DQA1*05:XX with DQB1*02:01

-DQA1*05:XX with DQB1*02:02

-DQA1*03:XX with DQB1*03:02

2. Homozygous (2 copies)

-DQA1*02:01 with DQB1*02:02

 

Gene pairs equivocal for celiac are:

1. Heterozygote (single copy)

-DQA1*02:01 with DQB1*02:02

2. Rare allele's types of DQ2 and DQ8 other than those listed above

 

All other gene pair combinations are considered nonpermissive for celiac.

 

There are reports that specific HLA-DQ2 and DQ8 combinations may confer different risks for the development of celiac disease.(1)

 

A recent publication from our group demonstrated that risk gradient of tissue transglutaminase (tTG) IgA positivity depends on specific HLA-DQ2 and DQ8 combinations.(2) For more information see Tissue Transglutaminase IgA positivity.

Cautions

Based on the catalog of common, intermediate, and well-documented alleles in the world population,(3), certain intermediate or common alleles in some ethnicities may not be resolved.

Method Description

LABType applies Luminex technology to the reverse sequence-specific oligonucleotide (SSO) DNA typing method. First, target DNA is polymerase chain reaction (PCR)-amplified using a group-specific primer. The PCR product is biotinylated, which allows it to be detected using R-phycoerythrin-conjugated streptavidin. The PCR product is denatured and allowed to rehybridize to complementary DNA probes conjugated to fluorescently coded microspheres. A flow analyzer identifies the fluorescent intensity of phycoerythrin on each microsphere. The HLA Class II allele or allele groups of the sample is determined by the positive and negative bead ID's using a computer software program. The assignment of the HLA typing is based on the reaction pattern compared to patterns associated with published HLA gene sequences.(Package insert: LABType SSO Typing. One Lambda; Version 04, 11/11/2019)

Report Available

3 to 8 days

Specimen Retention Time

14 days

Supportive Data

This figure shows the risk gradient of tissue transglutaminase (tTG) IgA positivity according to the HLA-DQ haplotype combination. Compared with patients who had non-permissive HLA-DQ heterodimers, patients who had HLA-DQ2 homozygosity (HLA-DQ2.5/DQ2.5, HLA-DQ2.5/DQ2.2, or HLA-DQ2.2/DQ2.2) showed increased odds for tTG-IgA positivity (OR =96.9; 95% CI, 58.3–147.9, p < .0001). Patients with 1 copy of HLA-DQ2.5 also had increased odds for tTG-IgA positivity, and, interestingly, the odds for patients who were compound heterozygous for HLA-DQ2.5 and HLA-DQ8 (OR =42.3; 95% CI, 25.2–71.0, p < .0001) were similar to those for HLA-DQ2.5 heterozygotes (OR =36.8; 95% CI, 23.3–57.9, p < .0001), suggesting that a single HLA-DQ8 haplotype may not provide additional risk for tTG-IgA positivity. HLA-DQ8 carriers also showed increased odds for tTG-IgA positivity.(2)

Forms

If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Test Request (T728) with the specimen.