ABSTRACT
Background How biologics affect psoriasis patients’ risks for SSTIs in a pragmatic clinical setting remains unclear.
Methods In a cohort of adult psoriasis outpatients (aged 20 years or older) who visited the Dermatology Clinic in 2010-2015, we compared incident SSTI risks between patients using biologics (users) versus nonbiologics (nonusers). We also estimated SSTI risks in biologics-associated time-periods relative to nonbiologics only in users. We applied random effects Cox proportional hazard models with propensity score-stratification to account for differential baseline hazards.
Results Over a median follow-up of 2.8 years (interquartile range: 1.5, 4.3), 172 of 922 patients ever received biologics (18.7%); 233 SSTI incidents occurred during 2518.3 person-years, with an overall incidence of 9.3/100 person-years (95% confidence interval [CI]: 8.1, 10.6). In univariate analysis, users showed an 89% lower risk for SSTIs than nonusers (hazard ratio [HR]: 0.11, 95%CI: 0.05, 0.26); the association persisted in a multivariable model (adjusted HR: 0.26, 95%CI: 0.12, 0.58). Among biologics users, biologics-exposed time-periods were associated with a nonsignificant 21% increased risk (adjusted HR: 1.21, 95%CI: 0.41, 3.59).
Conclusions Despite of adjusting for the underlying risk profiles, risk comparisons between biologics users and nonusers remained confounded by treatment selection. By comparing time-periods being exposed versus unexposed to biologics among users, the current analysis did not find evidence for an increased SSTI risk that was associated with biologics use in psoriasis patients.
List of abbreviations
- S. aureus
- Staphylococcus aureus
- SSTI
- skin and soft tissue infection
- MRSA
- methicillin-resistant S. aureus
- AD
- atopic dermatitis
- ICD-9-CM
- International Classification of Diseases, Ninth Revisions, Clinical Modification
- EMD
- Electronic Medical Database
- AST
- aspartate transaminase
- ALT
- alanine transaminase
- LDL
- low density lipoprotein-cholesterol
- AIC
- Akaike information criteria
- IQR
- interquartile range
- IR
- incidence rate
- CI
- confidence interval
- HR
- hazard ratio
- TH1
- type I helper T cell
- Treg
- regulatory T cell