Background/Purpose: Psoriasis/Psoriatic arthritis (PsO/PsA) often requires treatment with systemic agents. Some of these agents are associated with infectious adverse events. Few studies have described the background incidence of opportunistic infections (OIs) or Herpes zoster (HZ) infections, in a cohort of PsO/PsA patients.
Methods: We used the US Medicare dataset from 2006-2011 to identify a large cohort of PsA and PsO patients. We defined PsA and PsO as those with >1 rheumatologist-diagnosis code for psoriatic arthritis (ICD 9 696.0) or >1 dermatologist-diagnosis code for psoriasis (ICD 9 696.1) respectively, followed by a prescription for etanercept (ETA), cyclosporine (CIC), ustekinumab (UST), adalimumab (ADA), methotrexate (MTX) or ultraviolet light (UV) therapy. Patients had at least 6 months of continuous Medicare enrollment prior to the first date of exposure to these therapies. We excluded patients with organ transplantation, human immunodeficiency virus infection, advanced kidney and liver disease, or cancer with a 183-day period prior to cohort inception. Pairwise propensity scores (PS) were calculated and used to control for potential differences between comparator treatments. We used validated-claims based algorithms to identify OIs and HZ events among exposure groups. Patient exposures were censored at time of serious infection, death, end of study, loss of coverage, or 90 days following end of treatment exposure whichever came first. For OIs and for HZ, we calculated crude incidence rates in all exposure groups, and used Cox-proportional hazard regression models to calculate hazard ratios for these outcomes between exposure groups while adjusting for PS quintile.
Results: We identified 10,261 PsA individuals and 31,052 PsO individuals. Of the PsA cohort, there were fewer than 11 OI infections yielding an overall incidence rate of 1.5 (95% CI: 0.7-3.0) per 1,000 py, while the PsO cohort also had fewer than 11 OI infections with an overall incidence rate of 1.5 (95% CI: 0.6-3.0) per 1,000 py. For HZ, there were 82 HZ infections in the PsA cohort yielding an overall incidence rate of 16.1 (95% CI: 12.8-20.0) per 1,000 py, with the incidence rate ranging from 13.5 (95% CI: 4.3, 41.7) per 1,000 py for the UV therapy group to 20.0 (95% CI: 13.3-30.2) per 1,000 py for the ETA group. Of the PsO cohort, there were fewer than 391 HF infections with an overall incidence rate of 13.0 (95% CI: 11.8, 14.4) per 1,000 py. The incidence rate ranged from 11.1 (95% CI: 7.4-16.7) per 1,000 py for the CIC group to 14.3 (95% CI: 2.2-16.7) per 1,000 py for the MTX group. Rates of HZ infection were similar by exposure groups, but were higher than rates found in rheumatoid arthritis patients of the same age. For both the PsA and PsO cohorts, there were no significant associations by treatment type for either OI or the HZ infection, even when compared to the UV therapy group.
Conclusion: Among Medicare enrollees with PsA or PsO, biologic treatments were not associated with an increased risk of either OIs or HZ compared to non-biologic treatment (e.g. UV light).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-of-opportunistic-infection-and-herpes-zoster-infection-in-a-psoriasispsoriatic-arthritis-cohort/