Cytokine expression in temporal arteries: comparative analysis between patients with biopsy-positive giant cell arteritis, biopsy-negative giant cell arteritis and biopsy-negative without arteritis.

Objectives: To investigate whether expression of pro-inflammatory cytokines in the temporal artery may aid in differentiating biopsy-negative giant cell arteritis (GCA) patients from those with a negative biopsy without arteritis.
Methods: We investigated cytokine expression in temporal artery biopsy (TAB) of 54 consecutive patients: 17 with biopsy-positive GCA, 17 with biopsy-negative GCA, and 20 biopsy-negative without arteritis. We compared the expression rate of the following cytokines among these 3 groups of patients: interleukin-6 (IL-6), osteopontin (OPN), COX-2, and TNF-α.
Results: IL-6 was expressed in 13 (76%) patients with biopsy-positive GCA, 0 patients in biopsy-negative GCA, and 1(5%) patient with biopsy-negative without arteritis (p<0.05). OPN was expressed in 17 (100%) patients with biopsy-positive GCA, 2 (12%) patients with biopsy-negative GCA, and 0 patients with biopsy-negative without arteritis (p<0.05). Cox-2 was expressed in 16 (94%) patients with biopsy-positive GCA, 0 patients with biopsy-negative GCA, and 3 (15%) patients with biopsy-negative without arteritis (p<0.05). TNF- α was expressed in 17 (100%) patients with biopsy-positive GCA, 14 (82%) patients with biopsy-negative GCA, and 8 (40%) patients with biopsy-negative without arteritis (p<0.05).
Conclusions: IL-6, COX-2 and OPN are significantly more expressed in the presence of a positive TAB compared to a negative TAB. TNF-α is significantly more expressed in GCA patients compared to non-GCA patients. Thus, TNF-α expression may suggest a diagnosis of GCA despite a negative TAB. Further larger studies are needed to confirm these findings.