Calprotectin is a granulocyte and monocyte cytosolic protein that is released during activation of these cells. The plasma level of calprotectin is raised in various inflammatory conditions and correlates with disease activity in a wide range of rheumatic diseases. We wanted to investigate whether calprotectin may be useful as a measure of disease activity in polymyalgia rheumatica (PMR) and temporal arteritis (TA).
Forty-seven patients with PMR and/or TA were followed up to 3 years in a prospective longitudinal design. Plasma calprotectin was correlated with acute phase parameters, erythrocyte sedimentation rate (ESR), and peroral steroid usage before start of treatment and at four subsequent time intervals.
Thirty-three patients had PMR, 10 had TA, and four had both diagnoses. Calprotectin was highly correlated with the acute phase parameters and ESR during the study period. Calprotectin was significantly decreased after start of treatment with oral prednisolone, and correlated with the daily dosage of prednisolone (r = 0.36, p < 0.01).
Calprotectin plasma levels were significantly associated with acute phase parameters, ESR, and prednisolone usage in PMR and TA, indicating that calprotectin may be a good measure of disease activity in these conditions.