Seasonal incidence of biopsy-proven giant cell arteritis: a 20-year retrospective study of the University of California Davis Medical System.

OBJECTIVES

Giant cell arteritis (GCA) is a vasculitis that affects large and medium sized arteries. The aetiology of GCA is unknown and numerous risk factors have been proposed. In this article, we evaluate the incidence of biopsy-positive GCA in Northern California and assess for seasonal variation.

METHODS

We performed a retrospective review based on billing codes of temporal artery biopsies performed at the University of California, Davis from 2003 to 2014.

RESULTS

We identified 174 biopsies (119 female, 55 male). Of these, 21 positive biopsies were female while 8 were male. Although three times as many women had a positive biopsy compared to men, twice as many biopsies were performed on women. Women were not found to have a significantly higher risk of developing GCA over men. Patients with a positive biopsy averaged 76.4±8.9 years of age. The odds of having a positive biopsy increased significantly with age. Positive biopsies were significantly more likely to occur in the months of May through July than the rest of the year (p<0.028).

CONCLUSIONS

Our retrospective study is the first report of the seasonal incidence of biopsy-proven GCA in California. Our data suggest that increased age and summer months are risk factors for developing biopsy-proven GCA in our region.