Serum adenosine deaminase may predict disease activity in rheumatoid arthritis

To determine the relationship between serum adenosine deaminase (ADA) and disease activity, and to develop a new disease activity index based on serum ADA in rheumatoid arthritis (RA). Seventy RA patients were included. Disease activity based on Disease Activity Score 28-ESR (DAS28-ESR) and Disease Activity Score 28-CRP (DAS28-CRP) and serum ADA were measured. There were correlations when serum ADA compared with DAS28-ESR and DAS28-CRP. (R2 = 0.014, 0.175, respectively, P values < 0.00). New disease activity index was developed by replacing ADA with ESR and CRP in DAS28-ESR and DAS28-CRP. There were strong correlations when new model compared with DAS28-ESR and DAS28-CRP. (R2 = 0.94 and 0.95, respectively, P values < 0.00) The best new model values corresponding to DAS28-ESR values of 2.6, 3.2, and 5.1 were 2.79, 3.4, and 4.82, respectively; and new model values corresponding to DAS28-CRP values of 2.3, 2.7, and 4.1 were 2.1, 2.9, and 4, respectively. There were agreements when the new model compared with DAS28-ESR and DAS28-CRP for determination of patients in different disease activity categories. (Kappa = 0.81 and 0.71, respectively, P values < 0.00). The new disease activity index that applies serum ADA may help in predicting disease activity in RA.