Background Anti-Smith (Sm) antibody is highly specific antibody for systemic lupus erythematosus (SLE). We evaluated the association between anti-Sm antibody and disease activity in patients with new-onset SLE.

Methods Patients who were repeatedly tested for anti-Sm antibody at SLE diagnosis and within 12 months were included in this study. The clinical and laboratory profiles, and systemic lupus erythematosus disease activity index (SLEDAI) were collected at the time of anti-Sm antibody test. SLEDAI and laboratory variables associated with disease activity were compared between patients with and without anti-Sm antibody.

Results Of 92 patients who were tested for anti-Sm antibody at SLE diagnosis, 67 patients were followed up for presence of anti-Sm antibody at 6 months, and 67 patients were followed up at 12 months. Although the baseline SLEDAI was comparable in SLE patients with or without anti-Sm antibody, immunologic and hematologic disorder was more common in anti-Sm positive patients. Patients who showed positive result of anti-Sm antibody at 6 and 12 months had higher SLEDAI compared to patients with negative result (p=0.004 and 0.002 at 6 and 12 months, respectively). The changes in anti-Sm antibody for 12 months was significantly correlated with the changes of SLEDAI (p=0.029).

Conclusions Persistence of anti-Sm antibody for 12 months was associated with higher disease activity at the corresponding time. Follow-up of anti-Sm antibody can be useful to evaluate the remained disease activity in patients with new-onset SLE.

Funding Source(s): None