The outcome of a patient with giant cell arteritis (GCA) is closely related to the development of severe ischemic manifestations. In the current study we analyzed the implications of routine laboratory tests obtained at the time of diagnosis in the clinical spectrum of a series of 240 consecutive patients with biopsy-proven GCA at the single hospital for a defined population. We also examined whether the laboratory markers of inflammation may be predictors of severe ischemic manifestations (visual ischemic events, cerebrovascular accidents, jaw claudication, or large-artery stenosis of the extremities of recent onset), and their potential correlation. Anemia (hemoglobin <12 g/dL) was observed in 131 (54.6%) and thrombocytosis in 117 (48.8%) patients. Sixty-eight (28.3%) patients had leukocytosis. The percentage of patients showing a significant increase of alkaline phosphatase and hypoalbuminemia was similar (25% and 27.8%, respectively). The mean values of erythrocyte sedimentation rate (ESR) and C-reactive protein were 93 +/- 23 mm/h and 94 +/- 63 mg/L, respectively. A strong correlation among most laboratory markers of inflammation was observed. Anemia was more commonly observed in patients without severe ischemic manifestations (61.5% versus 48.9% in those with severe ischemic manifestation; p = 0.05) and in patients with constitutional syndrome or fever (p < 0.001). Patients with ESR greater than 100 mm/h exhibited more commonly constitutional syndrome (p < 0.001) and had a statistically significant reduction in the incidence of visual ischemic events (p < 0.025). Only 7 (22.6%) of the 31 patients who suffered permanent visual loss had an ESR at the time of disease diagnosis greater than 100 mm/h. However, in a multivariate logistic regression analysis, only anemia was found to be a negative predictor for the development of severe ischemic manifestations of GCA (odds ratio, 0.53; 95% confidence intervals, 0.30-0.94; p = 0.03). In conclusion, our results suggest that some laboratory markers of inflammation, in particular the presence of anemia, may negatively predict the risk of severe ischemic complications in GCA patients.