Severe infections in giant cell arteritis - incidence over time and relation to large vessel involvement and comorbidities, a population-based study.

Patients with giant cell arteritis (GCA) are considered to be at increased risk of infections. The objectives of this study were to investigate the risk of severe infections in different time intervals after the diagnosis of GCA, compared to the general population, and to explore potential predictors for severe infections including large vessel involvement (LVI). Patients with biopsy-proven GCA, diagnosed between 2002 and 2010 in Region Skåne, Sweden, were identified and each case compared with 4 age-, sex- and residence area-matched reference subjects. Aortic involvement and other LVI was identified by case record review. Data on severe infections (requiring hospitalization) were obtained from linkage to the Skåne Healthcare Register through 2011. Prevalent comorbidities at GCA diagnosis were identified using ICD-10 codes. Predictors of severe infection in patients with GCA were evaluated using Cox regression. In 516 patients with GCA (100 with LVI), 22.9% experienced severe infections (mainly pneumonia and urinary tract infections), incidence rate of severe infection episodes 9.65/100 person-years (py). The incidence was particularly high during the first six months after diagnosis (14.8/100 py, rate ratio compared to reference subjects 3.27; 95% CI 2.06; 5.11). Higher age, LVI and several pre-existing comorbidities were associated with severe infections. In multivariable analysis, aortic involvement was a significant predictor of severe infection (multi-adjusted hazard ratio 1.75; 95% CI 1.04; 2.94). Compared to reference subjects from background population, patients with biopsy-positive GCA have increased risk of severe infections, in particular in early disease. Age, comorbidities and aortic involvement may predict severe infections in GCA. Further prospective studies on this subject, including detailed assessment of LVI, are needed.