To evaluate the utility of erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) for the diagnosis of giant cell arteritis (GCA) and to determine the frequency of normal ESR and CRP at diagnosis of GCA.

All patients undergoing temporal artery biopsy (TAB) between 2000 and 2008 were identified. Only subjects with both ESR and CRP at the time of TAB were included. The medical records of all patients were reviewed.

We included 764 patients (65% women), mean age 72.7 (±9.27) years, who underwent TAB. Biopsy was consistent with GCA in 177 patients (23%). Elevated CRP and elevated ESR provided a sensitivity of 86.9% and 84.1%, respectively, for a positive TAB. The odds ratio of a concordantly elevated ESR and CRP for positive TAB was 3.06 (95% CI 2.03, 4.62), whereas the odds ratio for concordantly normal ESR and CRP was 0.49 (95% CI 0.29, 0.83). Seven patients (4%) with a positive TAB for GCA had a normal ESR and CRP at diagnosis. Compared with GCA patients with elevated markers of inflammation, a greater proportion of these patients had polymyalgia rheumatica symptoms (P = 0.008), whereas constitutional symptoms, anemia and thrombocytosis, were observed less often (P < 0.05).

CRP is a more sensitive marker than ESR for a positive TAB that is diagnostic of GCA. There may be clinical utility in obtaining both tests in the evaluation of patients with suspected GCA. A small proportion of patients with GCA may have normal inflammatory markers at diagnosis.