Objective: To investigate whether the addition of all serologically defined HLA antigens to a baseline model further influences the predisposition to disease progression in psoriatic arthritis (PsA).
Methods: Patients with PsA followed prospectively over 19 years were studied. Clinical and laboratory assessments of both active inflammation and clinical damage were performed at 6 month intervals according to a standard protocol. Progression of damage was defined as transition to higher damage states defined by the number of damaged joints. A model that provides estimates of the ratio of transition rates for an individual with the antigen versus one without, and examines the antigen effect on each of the 3 transition rates, was used. HLA antigens were examined in groups by loci under the assumption of common effects across transitions when added to the basic model. The significance levels were examined in comparison with Bonferroni type corrections. Likelihood ratio chi-squared statistics were used as a basis for the significance levels. In total, 292 patients with PsA were included in the study.
Results: Only HLA-B22 was added to the original model, which includes HLA-B39, providing risk for progression in early stages, HLA-B27 in the presence of HLA-DR7 providing risk for progression through all states, and DQw3 providing increased risk in the absence of DR7, while in the presence of DR7 it provides "protection." HLA-B22 provides protection from disease progression through all states.
Conclusion: This study extends our report that HLA antigens serve as markers for disease progression in PsA.