To investigate the association between specimen length and number of sections evaluated and TAB’s (temporal artery biopsy) diagnostic yield for GCA (giant cell arteritis). A pathologist reviewed all TABs performed for suspected GCA between January 1991 and December 2012. The blocks of all the inadequate and negative biopsies were recut, and further slides at deeper levels were stained with hematoxylin‐eosin to avoid missing inflammatory changes.

662 TABs were included (71% female; mean age, 73.2 years). 427 (65%) TABs were classified as negative and 235 (35%) positive for GCA. Compared with negative TAB, patients with positive TAB were older and more frequently female. There was no difference in post‐fixation TAB length between TABs negative and positive for GCA (mean 6.5 vs. 6.9 mm, p=0.068). Cuts of additional biopsy sections revealed inflammation at deeper levels in 26/408 (6.4%) TABs initially reported as uninflamed. The inflamed section was the second in 14 TABs, the third in 9, and the fourth in 3. Piecewise logistic regression identified 5 mm as the TAB length change point for diagnostic sensitivity. Compared with TAB length of <5 mm, age‐ and sex‐adjusted odds ratio for positive TAB in samples ≥5 mm long was 1.5 (95% CI 1.0‐2.0), p=0.032.

A post‐fixation TAB length of at least 5 mm should be sufficient to make a GCA histological diagnosis. To not miss inflammatory changes, at least three further sections at deeper levels should be evaluated in all negative TABs.