Abstract 705: Diagnostic reproducibility of Giant Cell Arteritis on Temporal Artery Biopsy Specimen : The GRACG Study
Phil Seo
Authors
Denis Chatelain1, Pierre Duhaut1, Robert Loire2, Sylvie Bosshard2, Hélène Pellet2, Jean-Charles Piette3, Henri Sevestre1, Jean-Pierre Ducroix1.
Background
Although rheumatologists rely on the interpretation of the temporal artery biopsy in the evaluation of a patient with giant cell arteritis, little effort has been expended towards standardizing the interpretation of these biopsies. Therefore, judgments about “positive” and “negative” temporal artery biopsies may depend significantly on local practice, and the interpretation of these samples may differ between institutions. This study attempted to assess the reproducibility of the assessment of the temporal artery biopsy among different pathologists.
Methods
This study included temporal artery biopsy samples from patients diagnosed with either giant cell arteritis or polymyalgia rheumatic from 1991 to 2006. All slides were independently reviewed by two pathologists who were blinded to the initial diagnosis. Pathologists were instructed to score each temporal artery biopsy into 1 of 5 categories: (1) active arteritis with giant cells, (2) active arteritis without giant cells, ( 3) healed arteritis, (4) arteriosclerosis, and (5) normal temporal artery. Pathologists were specifically instructed to examine samples for evidence of giant cells and healed arteritis, and agreement was assessed using kappa statistics.
Results
Four hundred thirty-three biopsies were reviewed. Kappa coefficients were calculated to assess agreement between the two blinded pathologists regarding a variety of criteria. For positive versus negative biopsy, the kappa coefficient was 0.86 (95% CI 0.81, 0.92). For categorization (using the classification described above), the kappa coefficient was 0.74 (95% CI 0.67, 0.80). For the presence of giant cells, the kappa coefficient was 0.80 (95% CI 0.56, 0.68). For healed arteritis versus “negative” temporal artery biopsy, the kappa coefficient was 0.74 (95% CI 0.53, 0.94).
Conclusions
Despite the lack of formal guidelines for the assessment of temporal arteries, agreement between pathologists is quite good. That said, pathologists disagreed in 14% of cases regarding positive versus negative temporal artery biopsies; disagreement increased when pathologists were asked to assess for the presence of multinucleated giant cells or healed arteritis.
Editorial Comment
Rheumatologists often feel somewhat uncomfortable treating a patient for giant cell arteritis after the temporal artery biopsy has been judged to be “negative.” This interesting abstract demonstrates that the temporal artery biopsy, while quite good, may not be foolproof for the diagnosis of giant cell arteritis. In many cases, disagreement was likely due to the fact that the characteristic finding was present on only on a limited number of sections. Therefore, in certain cases, a “negative” temporal artery biopsy may merit a second look, particularly when the diagnosis is not clear.
