HLA-DQ8 tag — secondary celiac susceptibility
A tag SNP for HLA-DQ8 has been detected (one copy).
You carry one copy of the second main immune system version linked to celiac disease.
HLA-DQ8 is the second principal celiac risk haplotype. About 5–10% of celiac patients carry DQ8 without DQ2. Most DQ8 carriers do not develop celiac.
HLA-DQ8 is the second main genetic factor in celiac. Between 5 and 10 in 100 people with celiac have DQ8 but not the more common DQ2 version. Most people with DQ8 never develop celiac.
What this means
HLA-DQ8 covers most of the remaining ~10% of celiac genetic risk not explained by HLA-DQ2.5. As with DQ2.5, presence of the allele is *necessary but not sufficient*: testing positive doesn't establish a diagnosis. The diagnostic value is largely in ruling celiac out — without DQ2 or DQ8, celiac is essentially impossible.
HLA-DQ8 accounts for most of the remaining roughly 10% of celiac genetic risk not explained by the more common HLA-DQ2.5 version. As with DQ2.5, having this version is *necessary but not enough on its own*: a positive result doesn't mean you have celiac. The real value of testing is in ruling celiac out — without either DQ2 or DQ8, celiac is essentially impossible.
Caveats
- High negative predictive value, low positive predictive value.
- Tag SNP correlation is strong but imperfect.
- Diagnosis requires clinical evaluation (tTG-IgA, possibly biopsy).