SCOTTSDALE, ARIZ. (FRONTLINE MEDICAL NEWS) – From enterocolitis to MRSA, serious infections are on the rise among inpatients with psoriasis, and psoriasis is an independent risk factor for serious infections, according to findings from large retrospective studies from the United States and the United Kingdom.

Inpatients with psoriasis in the United States also were at greater risk of serious infections, compared with nonpsoriatic inpatients at every time point studied, and serious infections were associated with increased hospital costs, length of stay, and risk of mortality, reported Derek Hsu, a medical student at Northwestern University, Chicago, and his associates. “Research is needed to determine how to reduce the risk of serious infections in patients with psoriasis,” the investigators emphasized.

Psoriasis affects some 7 million adults in the United States. Biologics, which are transforming the treatment landscape for moderate-to-severe psoriasis, “should reduce inherent infectious risk by controlling the inflammatory process and reducing disease severity, [but] these effects may be immunosuppressing and increase the risk of infection in other ways,” according to Mr. Hsu and his associates. For their study, they analyzed data for 2002-2012 from the Nationwide Inpatient Sample, which covers 20% of hospitalizations in the United States. They extracted validated ICD-9 codes for psoriasis and serious infections, and calculated costs of care after adjusting for 2014 inflation, based on the United States Consumer Price Index.

Overall rates of serious infection and rates of pneumonia, MRSA, septicemia, diverticulitis, enterocolitis, encephalitis, and any viral or fungal infection rose significantly among inpatients with psoriasis between 2002 and 2012 (all P-values less than .05). Predictors of serious infections among inpatients with psoriasis included diabetes mellitus, obesity, and being of non-Caucasian race or ethnicity, female, older than 60 years, and on Medicare or Medicaid, the researchers reported at the annual meeting of the Society for Investigative Dermatology.

Furthermore, after controlling for age, sex, and race, psoriasis was a significant risk factor for many different types of serious infections. Among these were cellulitis, herpes simplex virus, infectious arthritis, osteomyelitis, meningitis, influenza, encephalitis, septicemia, enterocolitis, MRSA, methicillin-sensitive Staphylococcus aureus infections, and Clostridium difficile. Further, inpatients with psoriasis were more prone to urinary tract infection, peritonitis or intestinal abscess, appendicitis, tuberculosis, and viral and fungal infections (all P-values less than .05). The average cost of hospital stay for inpatients with psoriasis was more than $2,200 greater when they were diagnosed with one or more serious infections than otherwise, and their average length of hospital stay was 2 days longer.

The study in the United Kingdom included nearly 200,000 patients with psoriasis and almost 1 million patients without psoriasis from The Health Improvement Network electronic medical record database. Between 2002 and 2013, patients without psoriasis developed an estimated 78.5 serious infections per 100,000 person-years, compared with 88.9, 85.7, and 145.7 serious infections per 100,000 person-years, respectively, for all psoriasis patients, patients with mild disease, and patients with severe disease requiring systemic or phototherapy, said Dr. Junko Takeshita and her colleagues at the University of Pennsylvania in Philadelphia. After controlling for many potential demographic and clinical confounders, psoriasis increased the risk of serious infection by about 21% (hazard ratio, 1.21; 95% confidence interval, 1.18-1.23). Patients with severe psoriasis had a 63% greater risk of infection than patients without psoriasis, compared with an 18% increase for patients with mild psoriasis.

The findings show “serious infection, particularly respiratory and skin or soft tissue infections, to be an important and common cause of morbidity among patients with psoriasis, especially those with more severe disease,” Dr. Takeshita and her associates said. Notably, the link between psoriasis and risk of serious infection persisted after excluding patients on immunosuppressive therapies, suggesting “that the greater infection risk is at least partially attributable to more severe psoriasis, itself,” they added.

The analysis of Nationwide Inpatient Sample data was funded by the Agency for Healthcare Research and Quality and by the Dermatology Foundation. The analysis of Health Improvement Network data was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases, which is part of the National Institutes of Health, and by the Dermatology Foundation. None of the investigators reported conflicts of interest.