HLA-DQ2.5 tag — celiac disease susceptibility
A tag SNP for HLA-DQ2.5 has been detected (one copy).
You carry one copy of the main immune system version linked to celiac disease.
HLA-DQ2.5 is the principal genetic risk factor for celiac disease. Around 90% of people with celiac carry DQ2.5, but only ~3% of DQ2.5 carriers develop celiac.
This is the single biggest genetic factor in celiac disease. About 9 in 10 people with celiac have this version, but only around 3 in 100 people who have it ever develop celiac themselves.
What this means
HLA-DQ2.5 and HLA-DQ8 together explain the great majority of celiac disease's genetic risk. Celiac is essentially impossible without one of them, which is why genetic testing has high *negative* predictive value but limited positive predictive value. If a clinician suspects celiac, blood tests (tTG-IgA) and possibly a biopsy are the diagnostic tools — genotype alone doesn't make the diagnosis.
HLA-DQ2.5 and HLA-DQ8 are two immune system versions that together explain almost all of the genetic risk for celiac disease. You can basically only get celiac if you have one of them — which is why this kind of testing is great at ruling celiac *out*, but not so great at ruling it *in*. Plenty of people carry these versions and never develop celiac. If a doctor suspects celiac, the actual diagnosis comes from blood tests (tTG-IgA) and sometimes a small bowel biopsy. Your genes alone don't make the diagnosis.
Caveats
- High negative predictive value, low positive predictive value — having the variant doesn't mean you have celiac.
- Tag SNP is a strong but imperfect surrogate for the actual HLA-DQ2.5 allele.
- Diagnosis requires clinical evaluation, not genotype alone.