P9. Giant cell arteritis--over diagnosed?

Abstract

Background: GCA is the most common vasculitis in the western world. It typically affects individuals greater than 55 years of age and has significant morbidity from its pathology and its treatment. There are no recent (after 2001) estimates of the occurrence in the UK. The UK general practice research database (GPRD) reported between 1990 and 2001 an incidence of 22/100,000 aged >55 years in a primary care. The aim of this study was to estimate the occurrence of GCA in the UK. Methods: All temporal artery biopsies performed at the Norfolk and Norwich University hospital between 2003 and 2009 were reviewed. Cases of GCA were included only after careful case notes review with all cases fulfilling 1987 ACR criteria. The general practice GP location was noted for each of the included cases. The GP location was grouped into standard local authority boundaries. In cases where the individual practice population lay on a local authority boundary, the practice was classified into the local authority area which held the majority of the registered patients. The population denominator was calculated from national 2011 census data at 252 400 people. Incidence was calculated for the last 3 years of the study since robust data recording allowed for assured inclusion of cases of GCA with negative biopsy. 95% CI were calculated using the Poisson distribution. Results: There were 325 temporal biopsies performed at the NNUH between the years 2003 and 2009. Subsequently 134 individuals were diagnosed with GCA (41.2%). The mean age at diagnosis was 75.6 years. 97 were women (72.4%). Patients with GCA were significantly older (mean difference 4.1 years CI=1.3 to 6.9, P=<0.05) and had a statistically significant higher ESR (mean difference 44 mm/h, CI=34 to 54, P=<0.001) compared with individuals without GCA who underwent temporal artery biopsy. There were 78 cases of GCA (15 biopsy negative-19.2%) diagnosed in this period (2007 to 2009). Four cases were excluded as they were from outside the denominator population. Of the remaining 74 cases of GCA came from 42 general practices in five local authority areas. The incidence rate per 100,000 was 9.8 (95% CI 6.4, 14.7) in people aged >50 years and was 17.1 (95% CI 10.7, 25.3) per 100,000 >65 years. Conclusions: The results reveal an estimate of 9.8 per 100,000 people aged >50 years. This is much lower than the estimate from the GPRD study carried out in 2001. Within the GPRD study only three out of a selection of 45 cases that were reviewed had a positive temporal artery biopsy (6.7%) and 10 cases (22.2%) were diagnosed and managed in primary care alone. These data suggest that in Norfolk at least 50% of cases of GCA are managed in the community without referral for temporal artery biopsy or specialist opinion to confirm the diagnosis before embarking on toxic glucocorticoid treatment. Disclosures: The authors have declared no conflicts of interest.