Abstract
Objective The aim of this study was to evaluate the changes and
diagnostic value of serum ADA activity in autoimmune diseases, including
systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), ankylosing
spondylitis (AS), and myasthenia gravis (MG).
Methods Serum ADA activity, including total ADA (tADA) and its isoenzymes
(ADA1 and ADA2), was determined in patients with different autoimmune diseases
(144 RA, 114 SLE, 55 AS, 68 MG). The changes in serum ADA activity in patients
were analysed. A receiver operating characteristic (ROC) curve analysis was
applied to evaluate the diagnostic performance of serum ADA activity.
Results Compared with healthy controls, the serum tADA activity in SLE
patients was significantly increased (p<0.001), while the serum tADA
activity in patients with RA, AS and MG did not change (p>0.05). The ROC
analysis showed that the optimal cut-off value of serum tADA activity for SLE
diagnosis was 10.5 U/L (79.8% specificity and
74.6% sensitivity; likelihood ratio (LR): 3.693; p<0.001).
Moreover, our results showed that there were no significant changes of ADA1 and
ADA2 activity in RA, AS and MG patients, while the serum ADA2 activity was
significantly increased in SLE patients. The ROC analysis showed that ADA2
activity could be used in diagnosing SLE with 75.4% specificity and
78.1% sensitivity (LR: 3.175). Based on the ROC curve analysis, serum
tADA activity (79.8% specificity and 74.6% sensitivity;
likelihood ratio (LR): 3.693) and ADA2 activity (75.4% specificity and
78.1% sensitivity; LR: 3.175) are unlikely to be used in diagnosing SLE.
Furthermore, there was a positive correlation between tADA activity and SLE
disease activity (r=0.303, p=0.010). Notably, serum tADA
activity in SLE patients with arthritis was higher than in patients without
arthritis (p=0.005), which suggests that tADA activity might be related
to lupus arthritis.
Conclusion These findings suggest that serum tADA and ADA2 activity might
play an important role in SLE progression.
Appearance of Systemic Lupus Erythematosus in Patients with Myasthenia Gravis following Thymectomy: Two Case Reports