Psoriasis and Serious Infections

Although psoriasis has been shown to be associated with risk factors for serious infections, the independent relationship between psoriasis and these infections is currently not well defined.

In order to examine this relationship, researchers conducted a cohort study of 69,315 individuals with psoriasis and 338,620 controls from the UK Clinical Practice Research Datalink as well as data from Hospital Episode Statistics and Office for National Statistics mortality records.

Overall, individuals with psoriasis were at a greater risk for serious infection than were those without psoriasis (20.5 per 1000 person-years vs 16.1 per 1000 person-years, respectively). The adjusted hazard ratio for serious infection in patients with psoriasis was 1.36 (95% CI 1.31-1.40).

Consultant360 reached out to study author Zenas Yiu, MBChB, PhD, NIHR Clinical Lecturer in Dermatology at the University of Manchester, to further discuss the results of the study.

Consultant360: Why is the relationship between psoriasis and serious infections something that was important to explore further?

Zenas Yiu, MBChB, PhD: We were interested in this relationship because this is a concern many people with psoriasis have expressed. The current studies suggest that there may be a link between having psoriasis and getting serious infections, but they were limited by several major design problems. We wanted to perform a study with robust methods to overcome some of the issues we saw in the current studies and try to find out whether psoriasis truly leads to a higher risk of getting serious infections.

C360: In your study, you examined the risk of hospitalization from any infection, respiratory infections, and soft-tissue and skin infections. How did you decide on these 3 outcomes? Were any other specific types of infections considered as potential outcomes before being included in the “any infection” category? (exp. Gastrointestinal, UTIs)

ZY: The definition of serious infections can be variable, but an agreed definition is that the infection is serious enough to warrant a visit to hospital. We therefore looked at hospitalization as a marker of infection severity. Respiratory and soft tissue / skin infections are the most common types of infections, and therefore we wanted to look at these separately to see whether people with psoriasis had a different predisposition to these types of infections. In particular, there is a theory that the biological changes associated with psoriasis may in fact protect against skin infections, which made us also want to focus on this outcome. We considered the other types of infections but decided to report on all other infections as a group to make sure the report was succinct.

C360: Did the type of infection (viral, bacterial, fungal) have any impact on your results?

ZY: We did not stratify by the type of infection as we believed that any of these infections would be important to consider for patients. Furthermore, viral infections, such as influenza, may often not be coded reliably in electronic health care records, and hence the precise type of infection is not reported.

C360: What knowledge gaps still exist in this area that future studies should concentrate on?

ZY: The main knowledge gap is to understand why the underlying inflammatory and biological changes in psoriasis lead to an increased, albeit to a small degree, risk of getting serious infection. This is particularly important now when the COVID-19 pandemic is still a huge problem in many areas of the world, and people with psoriasis want to know whether they are particularly susceptible to COVID-19 or not.

Reference:

Yiu ZZN, Parisi R, Lunt M, et al. Risk of hospitalization and death due to infection in people with psoriasis: a population-based cohort study using the clinical practice research datalink. Published online March 28, 2020. Br J Dermatol. doi: 10.1111/bjd.19052