['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.', 'Anti-U1 RNA antibody levels were measured quantitatively, using a nitrocellulose filter binding assay. Disease activity was measured with a validated SLE activity index.', 'All 9 major disease exacerbations were associated with peaks in anti-U1 RNA antibody level.'] Do changes in anti-U1 RNA antibody levels correlate with disease activity in patients with systemic lupus erythematosus overlap syndrome?