Synovial fluid adenosine deaminase and high-sensitivity C-reactive protein activity in differentiating monoarthritis

It is proposed that synovial fluid biomarkers may help in differentiating the type of arthritis. The aim of study is to determine whether synovial fluid adenosine deaminase (ADA) and high-sensitivity C-reactive protein (hs-CRP) can be useful in this regard. A total of 75 patients with knee monoarthritis that were admitted in Shahid Beheshti Kashan hospital in 2009 included in the study. There were 18 rheumatoid arthritis, 13 crystal-induced arthritis, 3 septic arthritis and 41 osteoarthritis. Inflammatory arthritis was diagnosed if more than 2,000 white blood cells existed in per milliliter of the synovial fluid. There was statistically significant difference in mean synovial fluid ADA and hs-CRP concentration between inflammatory (26.06 ± 8.96 IU/l, 12.72 ± 9.25 μg/ml) and non-inflammatory arthritis (14.8 ± 2.79 IU/l, 2.36 ± 2.7 μg/ml) (P values = 0.00, 0.00). There was statistically significant difference in mean synovial fluid ADA and hs-CRP concentration when rheumatoid arthritis (23.77 ± 4.58 IU/l, 10.47 ± 6.99 μg/ml), crystal-induced arthritis (22.76 ± 3.65 IU/l, 14.37 ± 11.58 μg/ml) and septic arthritis (49.66 ± 8.96 IU/l, 18.25 ± 5.37 μg/ml) were compared with osteoarthritis (14.58 ± 2.63 IU/l, 1.91 ± 1.31 μg/ml) (All P values = 0.00). There was statistically significant difference in mean synovial fluid ADA concentration between septic and rheumatoid arthritis and also between septic arthritis and crystal-induced arthritis (P values = 0.00, 0.00). This study showed that synovial fluid ADA and hs-CRP can properly differentiate inflammatory from non-inflammatory arthritis. Synovial fluid ADA is a useful marker in differentiating septic from rheumatoid and crystal-induced arthritis.