The combination of anti-CD74 and HLA-B27 was particularly interesting, with a post-test probability of 80.2% [assuming a 5% pre-test probability of axSpA in CBP (24, 25)], while being of 33.3% for IgA anti-CD74 alone and 28.8% for HLA-B27 alone. The gene discussed is CD79A; the disease is red color blindness.