Laboratory investigations useful in the evaluation of polymyalgia rheumatica (PMR) and giant cell arteritis (GCA)

The most useful investigation in supporting the clinical diagnosis of PMR/G CA is elevation of the erythrocyte sedimentation rate (ESR) or viscosity. A cute phase proteins, particularly CRF: are also elevated but in most cases are not more helpful than the ESR in either diagnosis or follow-up. The def initive investigation is the demonstration of giant cell arteritis histolog ically, usually from temporal artery biopsy. Elevation of alkaline phosphat ase of liver origin is seen in one-third to one-half of patients and may le ad to delay in diagnosis. Measurements of alpha 1-antichymotrypsin and IL-1 beta may be helpful in diagnosis and management but more studies are requi red.