Background/Purpose: To compare clinical characteristics, treatment, long-term follow-up and prognosis of two population-based cohorts of patients with biopsy-proven giant cell arteritis (GCA) from North America (American cohort) and South Europe (European cohort).

Methods: All patients residing in these two geographic regions with a new diagnosis of biopsy-proven GCA in 1986-2007 were retrospectively identified. Patients were followed from GCA diagnosis to death, migration or September 2011. Comparisons were performed using Chi-square and rank sum tests, Kaplan-Meier methods and Cox models. To account for differences in general population survival between the 2 geographic regions, survival in each GCA cohort was compared to expected rates obtained from age-, sex- and calendar year-specific lifetable rates for the general population of its region.

Results: The study included 110 patients in the American and 144 in the European cohort. Compared with the American cohort, patients from the European cohort were younger (mean±SD age 74.6±7.4 years vs 77.8±7.6, p=0.002), had longer duration of symptoms prior to diagnosis (median [IQR] 1.4 [1.0, 2.7] months vs 0.7 [0.2, 1.3], p< 0.001) and were more likely to have cranial symptoms (93% vs 86%, p=0.048), partial or complete unilateral or bilateral permanent vision loss (21% vs 6%, p=0.001), systemic symptoms (67% vs 46%, p=0.001) and polymyalgia rheumatica at or before GCA diagnosis (47% vs 26%, p< 0.001). ESR and CRP were higher (mean 88±29 mm/h vs 73±77, p< 0.001 and mean 89.0±60.2 mg/L vs 35.2±43.4, p< 0.001 respectively) and hemoglobin lower (mean 11.2±1.4 g/dl vs 11.8±1.4, p=0.004) in European than in the American cohort. Patients from the American cohort received a higher initial prednisone dose (mean 53.6±15.3 mg/day vs 49.5±12.8, p=0.001). There were no differences in relapse rates, cumulative glucocorticoid (GC) dosages at 1, 2 and 5 years, and time to first GC discontinuation.
Overall survival curves showed a better survival of patients with GCA from both study cohorts compared to expected rates obtained from age-, sex- and calendar year-specific lifetable rates for the general population of the respective regions (Figure 1A-B). As shown by survival curves, the mortality of patients with GCA was similar to the general population in the first 6 years from GCA diagnosis (SMR [95% CI] 1.07 [0.72, 1.53], log-rank p-value = 0.71 for the American cohort, and 0.91 [0.65, 1.24], log-rank p-value = 0.55 for the European cohort), but became significantly lower in both study cohorts after 6 years from GCA diagnosis (SMR [95% CI] 0.27 [0.11, 0.57], log-rank p-value < 0.001 for the American cohort, and 0.36 [0.19, 0.61], log-rank p-value < 0.001 for the European cohort). The most common cause of death was heart diseases in both the study cohorts, followed by cancer, pulmonary diseases, infection and stroke.

Conclusion: The clinical features at onset of GCA differ between patients from South Europe and North America. Geographical, genetic and/or environmental factors may contribute to the differences observed in this study. Improvement in survival for the GCA cohorts is a novel finding that will require further validation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-biopsy-proven-giant-cell-arteritis-in-north-america-and-south-europe-a-population-based-study/