Serum keratan sulphate levels rise in rheumatoid arthritis patients, but fall in ankylosing spondylitis patients compared with normal controls.

Serum levels of keratan sulphate (KS) were found to be significantly elevated in patients with destructive and predominantly seronegative rheumatoid arthritis (RA) compared with a control population. Levels in RA did not correlate with clinical or laboratory indices of joint activity or damage. Conversely levels were depressed in ankylosing spondylitis (AS) compared with controls.