In the univariable logistic regression analysis to investigate risk factors associated with progression to JoAS, the variables of age at disease onset, disease duration, morning stiffness, nocturnal pain, buttock pain, IBP, hip arthritis, enthesitis, baseline elevated acute-phase reactants (CRP and ESR) and MRI-positive sacroiliitis were statistically significant (p<0.05). This evidence concerns the gene CRP and Sacroiliac arthritis.