Plasma viscosity and the diagnosis of giant cell arteritis.

The level of plasma viscosity associated with the diagnosis of giant cell arteritis, and its use as a replacement for the erythrocyte sedimentation rate (ESR) is examined, by reviewing the records of 59 patients undergoing temporal artery biopsy. All patients with positive temporal artery biopsy had plasma viscosity above the upper limit of normal (1.72 mPa.s), range 1.88 to 2.28. There was a large group of patients with a possible diagnosis, supported by a raised plasma viscosity, who in the absence of a positive biopsy were not felt to have clinical disease requiring steroid treatment. The role of plasma viscosity appears to be similar to that of the ESR in the diagnosis of giant cell arteritis.