Test Details
Methodology
Genotyping for the DQA1 locus is performed using next-generation sequencing (NGS) of exon 2 and reported at G group resolution. A G group includes all alleles with identical nucleotide sequences encoding the antigen recognition site. Results are reported as "positive" or "negative." Positive indicates the presence of one copy (heterozygous) or two copies (homozygous) of the HLA-DQA1*05 variant allele.
Use
This test identifies the HLA-DQA1*05 variant. Carriers of this variant allele in either one copy (heterozygous) or two copies (homozygous) have a 75% higher risk of anti-infliximab (anti-IFX) or anti-adalimumab (anti-ADL) antibodies compared with noncarriers (relative risk for carriers, 1.75, 95% Cl, 1.37-2.25, according to Solitano et al in the latest systematic review and meta-analysis of 13 studies, including 3,756 patients for a median follow-up of 12 months).1
Noncarrier patients still developed immunogenicity, albeit at a lower incidence (20% vs 35%).1 Based on a 41% prevalence of variants (as found in predominantly Europeans and North Americans), a positive result on this test carries a positive predictive value (PPV) for immunogenicity of 30%. A negative result on this test indicates noncarrier status and does not mean the patient cannot develop anti-IFX or anti-ADL; it only suggests that the patient may be at decreased risk, with a negative predictive value (NPV) for immunogenicity of 80%.
The use of concomitant immunosuppressive therapy mitigates but does not eliminate the risk of immunogenicity in both HLA-DQA1*05 variant carriers and noncarriers.1 In two cohorts where proactive therapeutic drug monitoring (TDM) in infliximab (IFX) or adalimumab (ADL) was routinely performed, the presence of the HLA-DQA1*05 variant was not associated with increased risk of immunogenicity.2,3
Special Instructions
This test currently is not approved for use in New York state.
If you have questions, please call HLA customer service at 800-533-1037 for assistance in selecting the appropriate HLA test for the patient.
Ship the specimen to arrive in the laboratory between Monday and Friday.
|
This test currently is not approved for use in New York state. If you have questions, please call HLA customer service at 800-533-1037 for assistance in selecting the appropriate HLA test for the patient. Ship the specimen to arrive in the laboratory between Monday and Friday. |
Limitations
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Specimen Requirements
Specimen
Whole blood or buccal swabs
Volume
One adult tube or four buccal swabs
Minimum Volume
One pediatric tube or two buccal swabs
Container
Lavender-top (EDTA) tube or four buccal swabs in a sealed envelope (buccal swab kit). If submitting buccal swabs, please use kit provided by Labcorp. To obtain the buccal swab kit or to discuss other specimen types, please call 800-533-1037 or email HLACS@labcorp.com.
Collection Instructions
Standard phlebotomy or follow instructions on buccal swab kit
Stability Requirements
| Temperature | Period |
|---|---|
| Room temperature | Whole blood: 1 week Buccal swabs: >2 years |
Storage Instructions
Maintain specimen at room temperature. Do not refrigerate or freeze.
Causes for Rejection
Improper collection tube; mislabeled specimen
Footnotes
1. Solitano V, Facciorusso A, McGovern DPB, et al. HLA-DQA1*05 Genotype and Immunogenicity to Tumor Necrosis Factor-a Antagonists: A Systematic Review and Meta-Analysis. Clin Gastroenterol Hepatol. 2023 Nov;21(12):3019-3029.e5. PubMed 37061107
2. Colman RJ, Xiong Y, Mizuno T, et al. Antibodies-to-infliximab accelerate clearance while does intensification reverses immunogenicity and recaptures clinical response in pediatric Crohn's disease. Aliment Pharmacol Ther. 2022 Mar;55(5):593-603. PubMed 34935161
3. Spencer EA, Stachelski J, Dervieux T, Dubinsky MC. Failure to Achieve Target Drug Concentrations During Induction and Not HLA-DQA1*05 Carriage Is Associated With Antidrug Antibody Formation in Patients With Inflammatory Bowel Disease. Gastroenterology. 2022 May;162(6):1746-1748.e3. PubMed 35026235
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 167680 | HLA-DQA1*05 Anti-IFX,ADL Assoc | 57090-3 | 167678 | HLA-DQA1*05 Anti-IFX,ADL Assoc | 57090-3 | |
| 167680 | HLA-DQA1*05 Anti-IFX,ADL Assoc | 57090-3 | 167663 | DQA1 | 94495-9 | |
| 167680 | HLA-DQA1*05 Anti-IFX,ADL Assoc | 57090-3 | 167664 | DQA1 | 94495-9 | |
| 167680 | HLA-DQA1*05 Anti-IFX,ADL Assoc | 57090-3 | 167135 | HLA NGS Methodology | 49549-9 | |
| Order Code | 167680 | |||||
| Order Code Name | HLA-DQA1*05 Anti-IFX,ADL Assoc | |||||
| Order Loinc | 57090-3 | |||||
| Result Code | 167678 | |||||
| Result Code Name | HLA-DQA1*05 Anti-IFX,ADL Assoc | |||||
| UofM | ||||||
| Result LOINC | 57090-3 | |||||
| Order Code | 167680 | |||||
| Order Code Name | HLA-DQA1*05 Anti-IFX,ADL Assoc | |||||
| Order Loinc | 57090-3 | |||||
| Result Code | 167663 | |||||
| Result Code Name | DQA1 | |||||
| UofM | ||||||
| Result LOINC | 94495-9 | |||||
| Order Code | 167680 | |||||
| Order Code Name | HLA-DQA1*05 Anti-IFX,ADL Assoc | |||||
| Order Loinc | 57090-3 | |||||
| Result Code | 167664 | |||||
| Result Code Name | DQA1 | |||||
| UofM | ||||||
| Result LOINC | 94495-9 | |||||
| Order Code | 167680 | |||||
| Order Code Name | HLA-DQA1*05 Anti-IFX,ADL Assoc | |||||
| Order Loinc | 57090-3 | |||||
| Result Code | 167135 | |||||
| Result Code Name | HLA NGS Methodology | |||||
| UofM | ||||||
| Result LOINC | 49549-9 |