Psoriasis is a common skin disease affecting around 3% of the population of the UK. People with psoriasis suffer from patches of red, flaky skin that can appear in any part of the body. Many studies have found that having psoriasis was associated with having other medical conditions affecting the heart, the kidneys, and the liver, and these conditions, along with having sore and red skin, lead some people with psoriasis to worry about an increased risk of infection. However, we do not know whether having psoriasis is associated with getting infections that are serious enough to lead to an admission to a hospital.
A previous study in the Netherlands showed that patients with psoriasis do have a higher risk of serious infections, but this finding has not been thoroughly investigated or repeated in studies of patients of other nationalities. Understanding the risk of infection in patients with psoriasis is important because in addition to the risk of the disease, patients with psoriasis often have to take treatments to suppress the immune system, which may further increase this risk. On the other hand, scientists have shown that psoriasis is associated with increased production of molecules called anti-microbial peptides, which are thought to help the skin guard against infections. There are some suggestions, therefore, that having psoriasis may in fact be protective against infections of the skin.
Our aim is to examine whether the risk of serious infection is higher in patients with psoriasis, or whether patients with psoriasis are specifically protected against skin infections.
Our aim is to investigate whether patients with psoriasis are at an increased risk of hospitalisation due to infection, death due to infection and at a decreased risk of hospitalisation due to cellulitis. A matched cohort study will be used. Adult patients identified using a Read coded diagnosis of psoriasis between 01/04/2003 and 31/12/2016, and eligible for linkage to outpatient and inpatient HES and ONS records will be matched (on age, gender and practice) with 6 unaffected comparison patients. Selection will be restricted to patients registered with a contributing practice for at least one year and follow-up will end when the patient either dies, transfers out of the practice, last data collection, the end of the study period, or experiences the outcome of interest. The outcome of first hospitalisation due to infection; and infection-related mortality will be defined according to ICD-10 classifications. Cox regressions will be used to investigate whether patients with psoriasis have a higher risk of hospitalisation due to any infection or due to cellulitis specifically. Hazard ratios (HRs) will be generated with and without adjustment for potential confounders. Adjustment will be made for patient-level deprivation, body mass index, presence of co-morbidities including diabetes, COPD/Asthma, HIV/AIDS, alcohol intake, Charlson Comorbidity 7Index and smoking status. Missing data will be accounted for using multiple imputation.
The main outcomes of the study will be: 1. incidence of first hospitalisation due to infection (including the subcategories of respiratory infections; skin and soft tissue infections; and urinary tract infections); 2. Death due to infection. We will examine death and hospitalisation reasons according to the International Code of Diseases version 10 (ICD-10) code lists.
Darren Ashcroft - Chief Investigator - University of Manchester
Zenas Yiu - Corresponding Applicant - University of Manchester
Christopher Griffiths - Collaborator - University of Manchester
Mark Lunt - Collaborator - University of Manchester
richard warren - Collaborator - University of Manchester
Rosa Parisi - Collaborator - University of Manchester
HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation