Psoriatic arthritis incidence among patients receiving biologic medications for psoriasis: A nested case control study.

OBJECTIVE The objective of this study was to investigate the effect of biological treatments for psoriasis on the incidence of psoriatic arthritis. METHODS A retrospective cohort study using the electronic medical records of a large health maintenance organization. Patients who had received biological treatment for psoriasis and were not diagnosed with psoriatic arthritis before or at the time of biologic treatment initiation were included. Controls were matched by age at diagnosis, gender, time until treatment initiation, maximum BMI and smoking. The groups were different in most characteristics. Hence, a propensity score matching was implemented. The groups were compared via log rank test and a multivariable Cox regression. RESULTS Overall, 1326 cases were included; 663 patients that had received biological treatment and 663 that had not. The Kaplan-Meier curve for the propensity score matched groups reflected a statistically significant increased risk for PsA among the control group compared to the biological treatment group. The results of the multivariable Cox regression showed that the control group had a significantly higher risk for PsA compared to the biological treatment group (adjusted HR=1.39; 95%CI: 1.03-1.87). CONCLUSION This study demonstrates a statistically and clinically significant lower risk for developing PsA among patients with psoriasis that receive biologic medications. The results suggest considering treatment with biologic medications in patients that present with significant risk factors for PsA at an earlier stage of treatment.