P-selectin as a circulating molecular marker in rheumatoid arthritis with thrombocytosis

To compare plasma concentrations of soluble P-selectin (sP-selectin) in patients with rheumatoid arthritis (RA) and thrombocytosis with those with RA with normal platelet counts and healthy controls, and to explore the relationship between clinical and serological measures of disease activity.

Nineteen patients with RA with marked thrombocytosis, 20 with normal platelet counts, and 24 controls were enrolled. Ritchie articular index and morning stiffness were recorded as clinical markers of disease activity. Blood samples were collected for platelet count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and plasma sP-selectin determinations. Correlations between sP-selectin and clinical and serological markers of disease activity were noted.

Patients with RA and thrombocytosis compared to patients with normal platelet counts showed evidence of more active disease when ESR, CRP, morning stiffness, and Ritchie articular index were considered. The thrombocyte count in patients with RA with marked thrombocytosis revealed a positive correlation with CRP and Ritchie articular score. Plasma sP-selectin levels were found to be significantly higher in patients with RA compared to controls. sP-selectin levels were significantly higher in patients with RA with thrombocytosis compared to those with normal platelet counts, and positive correlations were observed between plasma sP-selectin levels and Ritchie index, morning stiffness, and thrombocyte counts in those patients.

Elevated plasma sP-selectin levels in RA could indicate the presence of a continuous underlying inflammatory stimulus. In addition, the augmented increase in patients with RA and thrombocytosis and its correlation with clinical activity may imply the cytokine-adhesion molecule interaction mediates the chronic inflammation of RA.