sensitivity and specificity of adenosine deaminase in diagnosis of juvenile idiopathic arthritis

background :juvenile idiopathic arthritis (jia) is one of the most common chronic rheumatic diseases in children with unknown etiology and pathogenesis. it also has no diagnostic test and its clinical diagnosis is made through ruling out other types of arthritis. the aim of this study was to evaluate the level of ada (adenosine deaminase) in the serum of jia patients and to compare it with that of patients with reactive arthritis (ra). evaluation of sensitivity and specificity of serum ada level in jia was another objective.   methods : the study included 120 children with jia (mean age= 7.6 ± 4.3 years) and 40 children with ra (mean age= 5.5 ± 3.1 years). the ada was measured in the active phase of both diseases.   results : the mean ada serum level was obtained as 15.8 ± 11.8 u/l in jia patients and 14.3 ± 7.5 u/l in ra patients. the difference was statistically insignificant (p=0.4). another finding of this study was the significant specificity (77.5%) of this laboratory parameter for jia in comparison with its low sensitivity (36.7%). positive predictive value was 83% and negative predictive value 29%.   conclusion : determination of ada serum levels is a noninvasive reliable and easy biomarker for diagnosis of jia and it can be used as alternative parameters representing disease activity.