A comparison of serum biochemistry in ankylosing spondylitis, seronegative and seropositive rheumatoid arthritis.

Abstract

Serum biochemistry of 31 patients with ankylosing spondylitis (AS) was compared to that of 80 patients with rheumatoid arthritis (RA) (ARA [American Rheumatologic Association] criteria), 30 of whom were negative for circulating rheumatoid factor and 50 of whom were seropositive. All patients were selected because of moderate to severe disease activity. All 3 groups had distinctive biochemical profiles. Total serum SH and Hb were particularly good discriminators between AS and RA. IgG, IgA and acute-phase reactants complemented the sheep cell agglutination test in discriminating between seropositive and seronegative RA. In active AS a normal erythrocyte sedimentation rate was often seen in the presence of an abnormal C-reactive protein (CRP) and plasma viscosity.