Bone sialoprotein (BSP) was quantified in synovial fluids and sera from rheumatoid arthritis (RA) patients to elucidate whether its release from bone relates to the degree of joint tissue destruction. Osteocalcin was assayed for comparison.
BSP and osteocalcin levels were determined by immunoassays of knee synovial fluids and of sera from RA patients who were selected on the basis of radiographic knee joint tissue damage.
Synovial fluid concentrations of BSP increased with increasing degrees of knee joint damage (rs = 0.6848, P < 0.001). Synovial fluid concentrations of osteocalcin did not relate to the degree of joint damage. Serum concentrations of BSP were increased, but did not relate to the degree of joint damage. Serum concentrations of osteocalcin were normal, but increased within the range of normal during progression of joint destruction (rs = 0.4567, P < 0.001).
Quantification of BSP in synovial fluid holds promise as a useful means of assessing the degree of tissue damage at the molecular level in patients with RA.