Total adenosine deaminase highly correlated with adenosine deaminase 2 activity in serum

We read with great interest the article published by Lee and colleagues1 presenting the potential diagnostic value of adenosine deaminase 2 (ADA2) in systemic juvenile idiopathic arthritis (sJIA) with macrophage activation syndrome (MAS). Their study examined ADA2 activity in children with inflammatory and immune-mediated diseases. By comparing normal ranges of ADA2 in healthy individuals, their finding identified the utility of plasma ADA2 activity as a biomarker of MAS. ADA2 activity were measures by a spectrophotometric assay in the presence of a selective inhibitor of ADA1, erytro-9-amino-β-hexyl-α-methyl-9-ethanol hydrochloride (EHNA). We support the views expressed by the authors that ADA2 detection could be helpful in the diagnosis of MAS in sJIA. Here, we would like to share with the authors our data of ADA activity detection. As we know, ADA contains …