Mortality in American veterans with the HLA-B27 gene

Abstract

Objective. To compare survival in American veterans with and without the HLA-B27 (B27) gene. Methods. Mortality was evaluated in a national cohort of veterans with clinically available B27 test results between October 1, 1999, and December 31, 2011. The primary outcome was the mortality difference between B27-positive and B27-negative veterans, adjusted for age, sex, race, and diagnoses codes for diseases that may have influenced both B27 testing and mortality, including psoriasis, inflammatory bowel disease, spondyloarthritis (SpA), and other types of inflammatory arthritis. The secondary outcomes were the adjusted mortality HR for B27+ and B27- veterans, in subgroups with and without SpA. Results. Among veterans with available B27 test results, 27,652 (84.7%) were B27- and 4978 (15.3%) were B27+. The mean followup time was 4.6 years. Mortality was higher in the B27+ group than in the B27- group (HR 1.15, 95% CI 1.03-1.27). Mortality was also higher in the B27+ subgroups with SpA (HR 1.35, 95% CI 1.06-1.72) and without SpA (HR 1.11, 95% CI 0.99-1.24), but the difference was significant only in the subgroup with SpA. Conclusion. B27 positivity was associated with an increased mortality rate in a cohort of veterans clinically selected for B27 testing, after adjustment for SpA. In the subgroup with SpA, the mortality rate was associated with B27 positivity, and in the subgroup without SpA, there was a nonsignificant association between B27+ and mortality.