LONDON – The survival of patients with giant cell arteritis has more than doubled in the past 20 years, according to the results of a population-based study presented at the European Congress of Rheumatology.
Comparing two cohorts of patients with giant cell arteritis (GCA) – one diagnosed between 1997 and 2004 and the other between 2005 and 2012 – researchers supported by Arthritis Research Canada found that the adjusted relative risks for death over the two time periods were 3.62 (95% confidence interval, 3.04-4.32) and 1.41 (95% CI, 1.15-1.74), respectively, when compared against individuals in the general population.
Dr. J. Antonio Avina-Zubieta
“The risk of death from GCA over time has decreased,” noted the principal study investigator Dr. J. Antonio Aviña-Zubieta in an interview ahead of the congress.
“We were not expecting such high mortality in the earlier GCA cohort [almost five times the general population]. GCA is a disease of older individuals, therefore the background risk for the individuals without GCA is already high, making it difficult to find statistically significant differences. In addition, we were not expecting such a dramatic improvement in the recent cohort, where the risk of death is approaching the baseline risk of the general population,” he observed.
Dr. Aviña-Zubieta, who is at the department of medicine at the University of British Columbia in Vancouver, and a scientist at Arthritis Research Canada, noted that improved mortality also was seen in individuals without GCA over the two time periods, but this was not as dramatic as in the GCA cohorts. “This suggests that at least some of the improvement in the GCA cohort is likely related to better care in general.”
Improved survival over time has been noted recently in several rheumatic diseases, such as systemic lupus erythematosus and rheumatoid arthritis, and Dr. Aviña-Zubieta’s research group wondered if the same might be true in systemic vasculitis.
“Given that GCA is the most frequent adult systemic vasculitis, we decided to test this question. Furthermore, given that our cohort is a population-based study, we thought that our result could be generalizable to the general population,” he said.
The study, which was funded by the Canadian Institutes of Health Research, involved obtaining data from an administrative health database on all newly diagnosed cases of GCA (n = 1,009) occurring between 1997 and 2012 in British Columbia, Canada. Cases were each matched by age, gender, and time of entry into the database to 10 non-GCA cases as controls (n = 10,009).
The mean age of participants in the GCA and non-GCA groups was 76 years, and 73% of participants in each group were female. As expected, individuals with GCA were more likely than those without the disease to have preexisting diseases such as hypertension (48.5% vs. 43.5%, P = .001), chronic obstructive pulmonary disease (15% vs. 11.4%, P less than .001), or angina (11.6% vs. 7%, P less than .001); to be taking medications; and to use health care resources to a greater extent.
Lindsay Belvedere
The definition used to define a case of GCA was quite strict according to Lindsay Belvedere, a research assistant at Arthritis Research Canada and a Master in Public Health student at Brigham Young University in Provo, Utah, who presented the study’s findings. Cases were required to have one ICD-9 or ICD-10 code for GCA given to them by a rheumatologist or after hospitalization or two ICD-9 or ICD-10 codes given on two separate occasions by a nonrheumatologist physician, and also they had to have received at least one prescription for glucocorticoids.
“This definition has been used in previous studies and been found to have a positive predictive value of 91%,” she observed. “To further increase the specificity of our case definition we excluded those who, following their diagnosis for GCA, received a diagnosis for another type of inflammatory arthritis such as psoriatic arthritis.” In addition, to ensure only incident cases were included in the cohort, patients with a GCA diagnosis prior to 1996 were also excluded from the dataset.
The early (1997-2004) versus the late (2005-2012) GCA cohort was found to have “considerably higher” mortality, with 373.7 versus 87.5 cases per 1,000 person-years. By comparison, there was a much smaller improvement in mortality during the two periods in the non-GCA cohort (75.9 vs. 48.6 cases per 1,000 person-years).
“These findings suggest that health care in general has improved, but more so in individuals with a serious disease such as GCA,” Dr. Aviña-Zubieta observed. Whether this is related to patients being diagnosed earlier, different treatment approaches, better management of complications, or better strategies to prevent complications remains to be tested, he said.