SMART-SLE: serology monitoring and repeat testing in systemic lupus erythematosus—an analysis of anti-double-stranded DNA monitoring

Disease activity monitoring in systemic lupus erythematosus (SLE) includes serial measurement of anti-double stranded-DNA (dsDNA) antibodies, but in patients who are persistently anti-dsDNA positive, the utility of repeated measurement is unclear. We investigated the usefulness of serial anti-dsDNA testing in predicting flare in SLE patients who are persistently anti-dsDNA positive.Data were analysed from patients in a multinational longitudinal cohort with known anti-dsDNA results from 2013 to 2021. Patients were categorised based on their anti-dsDNA results as persistently negative, fluctuating or persistently positive. Cox regression models were used to examine longitudinal associations of anti-dsDNA results with flare.Data from 37,582 visits of 3,484 patients were analysed. 1,029 (29.5%) of patients had persistently positive anti-dsDNA and 1,195 (34%) had fluctuating results. Anti-dsDNA expressed as a ratio to the normal cut-off was associated with the risk of subsequent flare, including in the persistently positive cohort (adjusted hazard ratio (95% confidence interval) 1.56 (1.30, 1.87) (p < 0.001) and fluctuating cohort (adjusted HR (95%CI) 1.46 (1.28, 1.66)), both for a ratio >3. Both increases and decreases in anti-dsDNA more than two-fold compared to the previous visit were associated with increased risk of flare in the the fluctuating cohort (adjusted HR(95%CI) 1.33(1.08, 1.65) p = 0.008) and the persistently positive cohort (adjusted HR (95%CI) 1.36 (1.08, 1.71) p = 0.009).Absolute value and change in anti-dsDNA titres predict flares, including in persistently anti-dsDNA positive patients. This indicates that repeat monitoring of dsDNA has value in routine testing.