Background/Purpose: Giant cell arteritis (GCA) is the most common type of vasculitis in adults aged 50 years or older. Although the substantial morbidity from infections in patients with GCA, partly due to immunosuppressive treatment, is well recognized, few studies have evaluated the incidence of severe infections compared to the general population. Even fewer have investigated the incidence of severe infection by time from GCA diagnosis compared to a reference population.

The objective of this study was to compare the risk of severe infection in different time intervals after GCA diagnosis to the general population.

Methods: Patients with biopsy-proven GCA, diagnosed between 2002 and 2010 were retrieved from a regional pathology register. They were compared with four reference subjects per case from the corresponding area, matched for age, sex and area of residence. Data on infections requiring hospitalization were obtained from linkage of the cases and the references to the regional healthcare register, through 2011. Using ICD-10 codes, twenty categories of infections were identified. Patients and reference subjects were censored at death or migration from the area. Incidence rates of severe infections in patients with GCA and reference subjects, stratified by follow-up time (0-6 months, 6-12 months, 1-2 years, 2-3 years, > 3 years), were estimated by dividing the number of severe infections in each time interval with the corresponding follow-up time (in years). The follow-up time started at date of diagnosis for patients (index-date for reference subjects) and ended at death or December 31, 2011. Rate Ratios (RRs) regarding severe infections, stratified by category of follow-up time, were calculated for patients with GCA vs. reference subjects. The 95% confidence intervals (CI) for incidence rates and RRs were estimated using the Poisson distribution ratio.

Results: Five hundred and sixteen patients with GCA were identified and compared to 3335 matched reference subjects. A total of 222 severe infections occurred in 118 patients with GCA. The cumulative incidence rate of severe infections was 8.5 % during the first year and 22.9 % over the entire follow-up.

The incidence rate in patients with GCA was highest during the first six months, 14.8/100 person-years (Table 1).

During this period, the rate was significantly increased compared to reference subjects (RR 3.27; 95% CI 2.06; 5.11) (Figure 1).

The rate of severe infections was numerically higher than that for the general population during the entire follow-up, but the difference reached statistical significance only during the first six months and after > 2 years of follow-up (Table 1, Figure 1).

Conclusion: The risk for severe infection is increased in patients with GCA compared to the general population, in particular during the first 6 months after diagnosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/increased-risk-of-severe-infections-in-early-giant-cell-arteritis-a-population-based-study/