Changes in anti–U1 RNA antibody levels correlate with disease activity in patients with systemic lupus erythematosus overlap syndrome

OBJECTIVE: To evaluate correlations between changes in anti-U1 RNA antibody levels and disease activity in 9 patients with systemic lupus erythematosus (SLE) overlap syndrome who were prospectively followed up for at least 3 years. METHODS: Anti-U1 RNA antibody levels were measured quantitatively, using a nitrocellulose filter binding assay. Disease activity was measured with a validated SLE activity index. RESULTS: All 9 major disease exacerbations were associated with peaks in anti-U1 RNA antibody level. CONCLUSION: These results seem to indicate that measuring anti-U1 RNA antibody levels can be useful for monitoring disease activity.