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.