Urinary sialyloligosaccharide excretion as an indicator of disease activity in rheumatoid arthritis.

Urinary trisaccharides containing sialic acid, urinary total sialic acid, and serum sialic acid were studied in 51 patients with rheumatoid arthritis (RA). The urinary excretion of sialyllactose and sialyl-N-acetyllactosamine was measured by quantitative gas chromatography. The output of sialyllactose was significantly greater in patients with RA (31.9 +/- 17.3 mg/24, SD) than in control subjects (15.9 +/- 5.4, P less than 0.001). The RA patients also had higher mean levels of urinary sialyl-N-acetyllactosamine (P less than 0.05), total urinary sialic acid (P less than 0.001), and serum sialic acid (P less than 0.001). Urinary excretion of sialyllactose was considerably higher in patients with active and aggressive RA and moderately higher in patients with moderate disease activity. Excretion in those with mild or almost inactive RA did not differ significantly from that in the controls. Linear regression analysis revealed a strong positive correlation between urinary sialyllactose levels and clinical disease activity (P less than 0.001), as well as between excretion of sialyllactose and sialyl-N-acetyllactosamine in RA. These results suggest that the urinary content of trisaccharides containing sialic acid is an indicator of disease activity of RA.