Clinical significance of synovial fluid total hemolytic complement activity

Total hemolytic complement (CH50) was measured in 174 synovial fluids (SF) to determine its diagnostic and and prognostic value. SF CH50 was reduced relative to serum CH50 in 61% of patients with rheumatoid arthritis and 60% of patients with crystal-induced arthritis. There was no correlation of SF CH50 levels with disease duration, SF leukocyte count, presence of IgM rheumatoid factor, or radiologic evidence of erosions.