CD74 and red color blindness: Using a cutoff of 0.52, anti-CD74 IgG antibodies were present in 127 out of 274 patients with axSpA and in 137 out of 286 patients with CBP (46.4% vs. 47.9%, p = 0.71) resulting in a PPV of 48.1%, a NPV of 50.3%, a LR+ of 0.97 and a LR- of 1.03.