Plasma viscosity in giant cell arteritis.

BACKGROUND Diagnosis of giant cell arteritis (GCA) is based on criteria of the American College of Rheumatology. However, not all GCA patients meet these criteria and treatment may be delayed in individual patients, leading to an increased risk of complications. METHODS In an observational study, we investigated acute phase response markers in GCA and non-GCA patients matched for erythrocyte sedimentation rate and CRP levels. RESULTS Plasma viscosity (PV) was significantly elevated in all GCA patients, but normal in non-GCA patients. CONCLUSIONS Our data suggest that PV may reflect a more specific component of the acute inflammatory response in patients with GCA. Analysis of PV may significantly contribute to a reliable diagnosis early in the course of the disease, particularly in patients with suspected GCA that do not meet current diagnostic criteria.