Effect of biopsy length on the rate of positive temporal artery biopsies.

OBJECTIVE To investigate the relationship between temporal artery biopsy (TAB) length and the diagnostic sensitivity for giant cell arteritis (GCA). METHODS TAB pathology reports were reviewed for histological findings and formalin-fixed TAB lengths. The patient's charts were reviewed for clinical data. TAB was considered positive if there was a mononuclear cell infiltrate in the vessel wall. Biopsy-negative GCA was diagnosed when patients fulfilled the American College of Rheumatology classification criteria, in addition to favorable rapid response to steroid therapy. Patients were divided into 3 groups according to the clinical and histological features: Biopsy-positive GCA, biopsy-negative GCA, and no GCA. RESULTS 305 TAB reports of 173 individuals were reviewed. When only GCA patients TAB-positive and TAB-negative were considered, TAB in the biopsy-positive patients was significantly longer than in biopsy-negative cases (p=0.008). The rate of positive biopsies was only 19% with TAB length of 5 mm or less, but increased to 71-79% with TAB lengths of 6-20 mm, and to 89% when TAB length was longer than 20 mm. Only 3% of positive biopsies were 5 mm or shorter, compared to 27% of TAB in biopsy-negative GCA cases (p<0.001). CONCLUSION TAB with post-fixation length shorter than 5 mm carries an increased biopsy-negative rate therefore longer TAB length is required for accurate diagnosis. Increasing post-fixation TAB length beyond 20 mm may further increase the rate of positive biopsies, although data were insufficient in that regard.