Patterns of disease activity in systemic lupus erythematosus

Objective. To describe patterns of systemic lupus (SLE) disease activity ov er time. Methods. Disease activity was measured in a prospective cohort of 204 conse cutive SLE patients followed up quarterly for 2.0-7.5 years (911 person-yea rs of followup), Physician's global assessment (PGA) and modified SLE Disea se Activity Index (M-SLEDAI; omitting serology) scores were plotted against time for each patient, Definitions for disease activity patterns were deve loped by consensus using these plots, and the proportion of total followup time represented by each pattern was calculated. Results. Three patterns of SLE activity were apparent: relapsing-remitting (RR), chronic active (CA), and long quiescent (LQ), The CA pattern was the most frequent for both the PGA and M-SLEDAI, representing 58% and 40% of to tal person-years, respectively, The least common pattern was LQ (PGA 16%, M -SLEDAI 25%), while the RR pattern was intermediate in frequency (PGA 26%, M-SLEDAI 35%). Average disease activity during RR periods tended to be mild , while that during CA periods was more likely to be moderately severe, The most common discrepancy between instruments was that the PGA depicted CA w hen the M-SLEDAI showed an RR pattern. The M-SLEDAI did not appear to captu re mild degrees of activity. Conclusion. SLE activity was readily classified into 1 of 3 patterns: RR,CA , or LQ, The CA pattern,vas most common, suggesting that significant morbid ity may arise from persistent disease activity. These findings may have imp ortant implications regarding the choice of outcome measures in SLE clinica l trials, since comparison of flare rates may not account for chronic disea se activity.