Abstract 704: Effect of Biopsy Length and Bilateral Sampling on the Rate of Positive Temporal Artery Biopsies
Phil Seo
Authors
G. S. Breuer, R. Nesher, G. Nesher
Background
How to assess patients for giant cell arteritis has been the subject of considerable debate. Although temporal artery biopsy has long been considered the gold standard for diagnosis, how the biopsy should be performed to optimize yield (while minimizing patient morbidity) is still not completely clear. This study examined two important questions—whether a unilateral biopsy is sufficient to make a diagnosis of giant cell arteritis, and what is the optimal length for the biopsy.
Methods
This retrospective study identified 305 temporal artery biopsy reports belonging to 173 patients with giant cell arteritis. In each case, the diagnosis was confirmed by chart review. Pathology reports were reviewed for the length of temporal artery biopsy and for histologic characteristics. A biopsy was considered positive if there was a mononuclear infiltrate in the vessel wall. Patients were said to have biopsy-negative giant cell arteritis when they met American College of Rheumatology criteria for the diagnosis of giant cell arteritis and had a rapid clinical response to glucocorticoids, but the temporal artery biopsy was not diagnostic.
Results
Fifty-one of the 80 patients with biopsy-positive giant cell arteritis underwent bilateral temporal artery biopsy; in 13/51 cases (25%), the temporal artery biopsy was positive only on one side. The mean length of the preserved temporal artery biopsy among patients with biopsy-positive giant cell arteritis was 12.7 +/- 5.6 mm; the mean length among patients with biopsy-negative giant cell arteritis was 10.1 +/- 5.4 mm. The sensitivity of a temporal artery biopsy of 6-10 mm was 31%; the sensitivity of a temporal artery biopsy larger than 10 mm was 50%. This difference was statistically significant (P=0.003).
Conclusions
The size of the temporal artery biopsy affects the rate of positive histological findings, with size >10 mm yielding 50% diagnostic sensitivity, compared to 31% sensitivity when size was 6-10 mm (p=0.003). With unilateral biopsies, the histological diagnosis may be missed in 12.5% (a half of 25%) of GCA cases. Therefore it is suggested that TAB needs to be performed bilaterally, and TAB size after formalin fixation should be more than 10 mm. Given that specimens shrink after fixation, the length of the biopsy should be at least 15 mm.
Editorial Comment
In many institutions, the surgeon looks to the rheumatologist for guidance on how the biopsy should be performed. This work emphasizes the importance of obtaining bilateral specimens of sufficient length when evaluating patients for giant cell arteritis. Because giant cell arteritis can lead to “skip lesions”, a single, short arterial segment is often not sufficient to exclude this diagnosis, and a bilateral temporal artery biopsy does increase yield significantly.
