Psoriasis was linked to increased risk of serious infection, with more severe disease associated with increased infection risk, in a study that used electronic medical records of patients in the United Kingdom.
The most common serious infections were lower respiratory tract, skin and soft tissue, and upper respiratory tract infections; and the most common opportunistic infection was tuberculosis, reported Junko Takeshita, MD, PhD, of the departments of dermatology and epidemiology at the University of Pennsylvania, Philadelphia, and her coauthors.
They identified 199,700 psoriasis patients and 954,315 healthy patients from THIN (the Health Improvement Network), a medical records database in the United Kingdom. Of the psoriasis patients, 187,258 had mild disease and 12,442 had moderate to severe disease; almost 70% of patients with moderate to severe disease were treated with methotrexate.
Adjusted hazard ratios for serious infection were 1.21 (95% confidence interval, 1.18-1.23) for psoriasis patients overall, 1.18 (95% confidence interval, 1.16-1.21) for those with mild psoriasis, and 1.63 (95% CI, 1.52-1.75) for those with moderate to severe psoriasis, Dr. Takeshita and her coauthors wrote in the Journal of Investigative Dermatology.
Among all psoriasis patients, the attributable risk of serious infection was 16.2 per 10,000 person-years, compared with 14.4 per 10,000 person-years among those with mild psoriasis, and 49.5 per 10,000 person-years, among those with moderate to severe disease.
The investigators also analyzed data from a nested cohort – the iHOPE (Incident Health Outcomes and Psoriasis Events) study – of 8,569 psoriasis patients, with mild (less than 3% of body surface area involvement) or moderate to severe disease (3% or greater BSA), and 83,540 matched patients without psoriasis.
The adjusted HR for serious infection was 1.21 (95% CI, 1.09-1.35) for all psoriasis patients, 1.16 (95% CI, 0.99-1.35) for those with mild disease, and 1.27 (95% CI, 1.10-1.47) for those with moderate to severe disease. When patients who had received immunosuppressive treatment were excluded from the analysis, hazard ratios were similar among the different psoriasis groups, at 1.18 for all psoriasis patients (95% CI, 1.05-1.32), 1.15 among those with mild disease (95% CI, 0.99-1.34), and 1.21 for those with moderate to severe disease (95% CI, 1.03-1.42).
“Importantly, the risk of serious infection was observed to be similar in both the full THIN and iHOPE cohorts with the exception of the moderate to severe psoriasis subgroup among whom the risk of serious infection was attenuated but still significantly elevated in the iHOPE versus full THIN cohort,” they observed.
In the THIN cohort, the most common opportunistic infection “by far” was tuberculosis, with incidence rates of 1.05, 0.94, and 3.00 per 10,000 person-years among all psoriasis patients, patients with mild disease, and patients with moderate to severe disease, respectively, compared with 1.15 for those without psoriasis.