To determine the impact of prior corticosteroid treatment on temporal artery biopsy (TAB) yield to establish the diagnosis of giant cell arteritis (GCA).
Retrospective study of a consecutive cohort of 78 patients clinically diagnosed and managed as GCA, who received corticosteroids before TAB.
Among the 78 patients, TAB was positive in 57 (73%) and negative in 21 (27%). No significant differences in the length of the specimen were found between the positive and negative biopsies. We grouped patients according to treatment duration before TAB. In those with newly diagnosed GCA treated with high-dose steroid therapy, the biopsy results were positive in 78% (35/45) of patients treated for less than 2 weeks, in 65% of those treated for 2 to 4 weeks (13/20), and in 40% of those treated for more than 4 weeks (2/5). We also observed 8 patients that developed GCA on a background of a prior history of polymyalgia rheumatica (PMR); in this group biopsy was positive in 88% of the cases, after a median duration of treatment of 180 +/- 172 days and an average daily dose of 7.1 +/- 1.4 mg/d.
The performance of TAB should not delay the prompt institution of steroid therapy on diagnosis of GCA, since the diagnostic yield of TAB seems valuable within 4 weeks of starting high-dose steroid treatment. In patients that developed GCA on a background of a prior history of PMR, a late TAB is also generally informative despite long-term treatment with low doses of corticosteroids.