OBJECTIVE: In contrast to relapsing-remitting patterns, persistently active disease (PAD) is a disease activity pattern in patients with systemic lupus erythematosus (SLE) that is inadequately studied. We sought to identify the frequency and determinants of flare and PAD in SLE. METHODS: Flare was defined using the Safety of Estrogens in Lupus Erythematosus National Assessment version of the Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI flare index), and PAD was defined as an SLEDAI-2K score of ≥4, excluding serology only, on two or more consecutive visits with a maximum six-month interval. Multivariable logistic regression was used to develop predictive models for flare and PAD, which were tested in an independent validation subset. RESULTS: Among 3,811 patients over 2.8 (interquartile range 1.0-5.3) years of follow-up, 2,142 (56.2%) experienced flare and 1,786 (46.9%) had PAD, with 368 (9.7%) experiencing PAD but not flare. The most common flare features were nephritis and arthritis, whereas PAD was most commonly characterized by renal or mucocutaneous activity. After adjusting for prednisone dose and use of antimalarials and immunosuppressants, low gross domestic product in country of residence, smoking, arthritis, nephritis, and low complement levels were predictive for flare, whereas being in a low disease activity state for ≥50% of follow-up time (LLDAS50) was a protective factor. Renal activity and higher time-adjusted mean SLEDAI-2K were predictive of PAD, whereas LLDAS50 was protective. The models developed gave 72.1% and 83.8% correct classification of flare and PAD, respectively, in the validation cohort. CONCLUSION: Both flare and PAD are common disease activity patterns in SLE
both predict organ damage accrual but differ in disease features and predictive factors. Because 9.7% of patients experience PAD but not flare, flare measures alone do not adequately capture all patients in whom disease control is suboptimal.