Serum markers associated with disease activity in giant cell arteritis and polymyalgia rheumatica.

OBJECTIVE To compare multiple serum markers for their ability to detect active disease in patients with GCA and in those with PMR. METHODS Twenty-six markers related to immune cells that may be involved in GCA and PMR were determined by ELISA and multiplex assay in the serum of 24 newly diagnosed, untreated GCA/PMR patients, 14 corticosteroid (CS)-treated GCA/PMR patients in remission and 13 healthy controls. Receiver operating characteristic analysis with area under the curve and Spearman's correlation coefficients were performed. RESULTS Serum B-cell activating factor (BAFF), CXCL9 and IL-6 were increased in newly diagnosed GCA and PMR patients. Serum CCL2, CCL11, IL-10 and sIL-2R were modulated in GCA patients only and CXCL10 in PMR patients only. BAFF, CXCL9 and IL-6 accurately distinguished newly diagnosed GCA and PMR patients from healthy controls, as shown by area under the curve > 0.80. Upon CS-induced remission, serum BAFF and IL-6 decreased significantly in both GCA and PMR patients, whereas CXCL9 remained high. Serum BAFF and IL-6 correlated strongly with ESR and CRP in GCA and PMR patients. CONCLUSION Among the serum markers tested, BAFF and IL-6 showed the strongest association with disease activity in both GCA and PMR patients. The diagnostic value of these markers should be evaluated in larger, longitudinal studies with GCA and PMR patients, and in patients with infections or other inflammatory conditions.