Background: Giant cell arteritis (GCA) afflicts older adults, who may have age- and comorbidity-related risks for infection, and is treated with glucocorticoids and other immunosuppressants that might increase the risk of serious infections.

Objectives: To examine GCA treatment patterns and rates of serious infections in two real-world cohorts in the U.S.

Methods: Using claims data from two U.S. health insurance databases, Medicare (public, 2007-2017) and MarketScan (commercial, 2015-2019), we selected a cohort of patients with GCA based on a validated claims-based algorithm requiring ≥2 diagnosis codes for GCA plus dispensing of high-dose oral glucocorticoid (PPV 84.8%) [1]. The Medicare cohort included Medicare enrollees aged ≥65 years with GCA who were treated at a large Massachusetts-based healthcare system; the MarketScan cohort included a nationwide sample of GCA patients aged ≥50 years. GCA index date was the date of 1 ^st glucocorticoid prescription. We assessed baseline comorbidities in the year prior to index date. Immunosuppressants and prophylactic antibiotics dispensed within 30 days of index date were recorded. Influenza vaccine administration in the year after index date was identified. We calculated the incidence rate of serious infections, defined as infections requiring hospitalization, after index date through end of cohort follow-up (12/31/17 in Medicare; 12/31/2019 in MarketScan), disenrollment, or death.

Results: The Medicare cohort included 734 patients, 28% male, mean age 77.1 (SD 7.4); the MarketScan cohort included 1022 patients, 30% male, mean age 68.4 (SD 10.9). The most common comorbidity was hypertension (80% Medicare; 72% MarketScan) followed by hyperlipidemia, cancer, coronary artery disease, and diabetes ( Table 1 ). High-dose prednisone was the most common initial treatment; a small percentage received tocilizumab within 30 days of index date. Prophylaxis against pneumocystis pneumonia was similar in Medicare (13%) and MarketScan cohorts (10%). Influenza vaccination was more common in the Medicare (56%) than MarketScan (22%) cohort in the year after GCA index date. During the mean follow-up time of 2.6 (SD 2.5) years in Medicare and 1.5 (SD 0.9) years in MarketScan, 27.9% of the Medicare and 7.2% of MarketScan patients developed serious infections: incidence rate per 100 person-years = 10.7 (95% CI 9.3, 12.2) in Medicare and 6.3 (95% CI 5.0, 7.9) in MarketScan.

Conclusion: In these 2 real-world GCA cohorts in the US, over 25% of Medicare and 7% of MarketScan patients developed serious infection during follow-up. The incidence rate of serious infection was similar to ANCA-associated vasculitis [2]. Use of prophylactic antibiotics and influenza vaccination was suboptimal among GCA patients.

REFERENCES:

[1]Lee H, et al. ACR Open Rheum 2020 (in press).

[2]Rathmann J, et al. Rheumatology 2020; doi: 10.1093/rheumatology/keaa699.

Disclosure of Interests: Sara Tedeschi: None declared, Yinzhu Jin: None declared, Seanna Vine: None declared, Hemin Lee: None declared, Attila Pethoe-Schramm Employee of: F. Hoffmann-La Roche, Vincent Yau Employee of: F. Hoffmann-La Roche/Genentech, Seoyoung Kim Grant/research support from: Roche, Pfizer, AbbVie and Bristol-Myers Squibb