The Incidence and Mortality rates of Giant Cell Arteritis in Southern Norway are lower than Previous Reported

Background/Purpose

Giant cell arteritis (GCA) is the most common form of vasculitis. The highest incidence rates of GCA have been reported from Southern Norway (29-32/ 100000 >50 years and mortality rates has been reported not to be different from the background population. However, data are from the end of 80’s to the early 90’s and no recent reports exist.

The aim of this study was to examine the incidence and standardized mortality ratios (SMR) of GCA in Southern Norway in the period of the last 13 years.

Methods

GCA patients were identified by using the hospital records during the years 2000-2013. The ICD-10 coding system (M31.5- 6) was used to identify the patients and the diagnoses were carefully verified. In addition, a retrospective study of the archives of the Department of Pathology was conducted, in order to identify patients with biopsy that were not registered by the ICD-10 system. SMR was calculated by using the death rates of the Norwegian population per 100 000.

Results

Mean age (95% CI) among the 212 identified GCA patients was 73.2 (72.0-74.4) years. Among them, 60 were males [mean age 73.4 years (71.0-75.7)] and 152 females [mean age 73.2 years (71.8-74.5)]. One-hundred fifty-five patients (73.1%) had a positive biopsy of the temporal artery, 42 patients (19.9%) a negative and in 15 patients (7.0%) biopsy was not performed. All the patients with a negative or not performed biopsy satisfied the ACR classification criteria for GCA.

The incidence rate for GCA was 17.2 per 100 000 >50 years (males 10.4 and females 23.4). The incidence rate of the biopsy-proven GCA was 12.6 per 100 000 >50 years. The yearly distribution of the incidence rates of GCA in Southern Norway is displayed in figure 1.

Among the 212 GCA patients, there were 52 deaths during the period 2000-2014. The overall SMR was 0.5 (95%CI 0.3- 0.6) [0.5 for males (95%CI 0.3- 0.7), and 0.4 for females (95%CI 0.3- 0.6)]. For biopsy-proven GCA the SMR rates were 0.7 (95%CI 0.4-1.0) for males and 0.4 (95%CI 0.2- 0.5) for females.

Conclusion

The incidence rate of GCA in Southern Norway during the years 2000-2013 is 45 % lower than this reported in previous studies. However, a rising tendency of the incidence rates has been noticed at the last 5 years (fig 1). Interestingly, the mortality of GCA patients appears to be lower compared to the background population. Better quality of health care in this group of patients could be a reason.

Fig 1