Background Giant cell arteritis (GCA) is the most common form of systemic vasculitis. The highest incidence rates of GCA worldwide have been reported from Southern Norway [32.8/100 000 aged>50 years (biopsy proven GCA 29/100 000 aged>50 years)]1,2. However, these data are from the end of 80's to the early 90's and no reports exist from the recent years. A latest report from Sweden indicates that the incidence rate of biopsy-proven GCA may have decreased over time3.
Objectives The aim of the present study was to examine the incidence rate of GCA in Southern Norway during the past 7 years.
Methods The patients were identified in the hospital electronic medical records by using the ICD-10 codes for GCA (M31.5- 6) and by searching in the electronic biopsy archives of the Department of Pathology during the years 2006-2012. Identified patients with a verified GCA diagnosis after reviewing the medical and the biopsy records were included. Incidence rates were calculated by using the mean population of Southern Norway aged ≥50 years during the period 2006 to 2012.
Results One-hundred and thirty-five GCA patients (mean age 73.6 years, 95% CI 72.0-75.1) were identified during the study period. Among them, 40 were males (30%) (mean age 72.6, 95% CI 69.3-75.9) and 95 females (70%) (mean age 74.0, 95% CI 72.3-75.7). The incidence rates for GCA was 21 per 100 000 aged>50 years (males 13.1 and females 27.9). Ninety-six patients (72.7%) had a positive biopsy of the temporal artery, 30 patients (22.2%) a negative and in 8 patients (6.6%) biopsy was not performed. All the patients with a negative or not performed biopsy satisfied the ACR classification criteria for GCA. Among patients with biopsy proven GCA the incident rate was 14.8 per 100 000 aged>50 years.
Conclusions The incidence rate of GCA in Southern Norway during the years 2006-2012 is approx. 30% lower than reported in previous studies. Particularly for patients with biopsy-proven GCA, the incidence rate was reduced 50% than earlier reported from the same region. Temporal variations could be an explanation for the lower incidence rates reported in this study. However, the lower rates could also be a sign of a true shift in GCA incidence rates in Scandinavia.
Haugeberg G, Paulsen PQ, Bie RB. Temporal arteritis in Vest Agder County in southern Norway: incidence and clinical findings. J Rheumatol 2000;27:2624-7.
Gran JT, Myklebust G. The incidence of polymyalgia rheumatica and temporal arteritis in the county of Aust Agder, south Norway: a prospective study 1987-94. J Rheumatol 1997;24:1739-43.
Mohammad AJ, Nilsson JA, Jacobsson LT, Merkel PA, Turesson C. Incidence and mortality rates of biopsy-proven giant cell arteritis in southern Sweden. Ann Rheum Dis 2014.
Disclosure of Interest None declared