HLA-B and Sacroiliac arthritis: Likewise, HLA-B*35 was found in 28.52% of SpA patients versus 26.04% of controls (p = 0.4085; RR = 1.10 [0.89–1.35]), and was particularly frequent in patients with inflammatory back pain (29.19%), radiographic sacroiliitis (23.33%), arthritis (28.97%), enthesitis (24.39%), and psoriasis (33.33%), as well as those with elevated systemic inflammatory markers (34.62%) (Table S2).