To make a histologic diagnosis of giant cell arteritis (GCA), a post-fixation temporal artery biopsy (TAB) length of ≥5 mm should be sufficient, according to study results published in Arthritis Care & Research. In addition, to account for inflammatory changes, at least 3 further sections at deeper levels should be examined in all negative TABs.
While TAB is considered the gold standard for the diagnosis of GCA, in up to 40% of patients with GCA, TAB results are negative. Since there are no data on the optimal TAB length and number of sections to make an accurate diagnosis of GCA, the objective of the current study was to determine the association between TAB length and number of sections evaluated and the diagnostic yield of TAB for GCA.
All patients who underwent TAB between January 1991 and December 2012 for suspected GCA at the Santa Maria Nuova Hospital in Florence, Italy, were included in the study. Researchers considered uninflamed TABs and TABs with evidence of periadventitial and/or adventitial inflammation as a negative biopsy for GCA.
The study included 694 TABs, of which 32 were determined to be inadequate and were excluded from the study. Of the adequate TABs, 427 (65%) were negative for GCA (382 uninflamed and 45 with evidence of periadventitial and/or adventitial inflammation), and 235 (35%) were positive.
The mean post-fixation TAB length was 6.6 mm (range, 1-40 mm), and median number of sections evaluated was 3 (range, 1-33). Researchers identified no difference in post-fixation TAB length between positive and negative biopsies (P =.068). However, the number of sections evaluated was lower with positive compared to negative TABs (P <.0001).
In 26 of 408 TABs (6.4%) that were initially concluded as negative, additional biopsy sections revealed inflamed sections at deeper levels, in most cases there was an inflammation restricted to periadventitial and/or adventitial tissue without extension to the media.
The optimal cutoff for the best diagnostic sensitivity of TAB was at a post-fixation specimen length ≥5 mm vs <5 mm. In a multivariate analysis, the odds ratio for obtaining a positive TAB was 1.453 (95% CI, 1.033-2.043; 38.3% vs 30.8% positive TABs, respectively).
Study limitations included the fact that the researchers did not differentiate between biopsy-positive and -negative patients with GCA, and they did not account for corticosteroid treatment at the time of TAB.
“[O]ur findings suggest that TAB length is potentially less important than has been thought when patients are accurately selected and TAB carefully examined. A post-fixation TAB length of at least 5 mm should be sufficient to make a histological diagnosis of GCA,” the researchers concluded.
Muratore F, Boiardi L, Cavazza A, et al. Association between specimen length and number of sections and diagnostic yield of temporal artery biopsy for giant cell arteritis. Published online August 2, 2020. Arthritis Care Res (Hoboken). doi:10.1002/acr.24393