Objectives. To estimate the effect of SLE disease activity, observed over a 12-month period, on the risk of irreversible organ damage and mortality, adjusted for potential confounding factors.
Methods. Patients were enrolled into a prospective cohort study and followed up from 1991. This study retrospectively analyses the data captured in the prospective cohort study. The study population consisted of 350 patients with SLE (meeting four or more of the revised ACR criteria) enrolled at University College Hospital, London lupus clinic. Disease activity was assessed during the observation year using the classic BILAG system and a mean total BILAG score was calculated for that time period. Organ damage outcomes, assessed over a subsequent follow-up period, were based on SLICC/ACR damage index scores and included new damage overall and by specific organ systems (renal, CNS or cardiovascular/musculoskeletal/pulmonary systems) or reaching a serious level of damage (SDI ≥ 3). Adjusted hazard ratios (HRs) for the association between disease activity and subsequent organ damage or mortality were calculated using Cox proportional hazards regression.
Results. Disease activity as measured by mean total BILAG score was associated with mortality (HR = 1.15, P = 0.008), new organ damage (HR = 1.08, P = 0.009) and CV/pulmonary or musculoskeletal damage (HR = 1.11, P = 0.007) after adjustment for age, sex, ethnicity, SLE duration, steroid exposure level, NSAID, anti-malarial or immunosuppressant use, renal activity and complement C3 or anti-dsDNA levels. Of these adjustment factors, age, renal activity, immunosuppressant use and pre-existing organ damage were additional independent predictors.
Conclusions. Disease activity as measured by global BILAG score during a 12-month observation period predicts the risk of subsequent organ damage and mortality after adjustment for key covariates.