Background/Purpose:

The Systemic Lupus International Collaborating Clinics (SLICC)/American College of Rheumatology (ACR) Damage Index (SDI) assesses irreversible damage in SLE and a higher SDI score predicts further damage and mortality.  Glucocorticoid (GC) use, a modifiable risk factor, has been associated with increased total SDI score and specific individual damage items. In a previous consensus exercise we categorised SDI items according to their likely association with GCs. Our aim was to explore the accrual of total and GC-related damage in a large international inception cohort.

Methods:

From 2000-11, we recruited patients within 15 months of developing four or more 1997 American College of Rheumatology (ACR) criteria for SLE. The SDI was completed at enrolment (if >6 months from diagnosis) and at each annual assessment. Total SDI scores in the cohort over time were assessed using descriptive statistics (point estimates of the mean) and the cumulative incidence of SDI items (grouped according to systems or likely steroid association) was calculated using Cox proportional hazard regression.   

Results: The mean (point estimate) SDI increased over time from 0.45 at assessments occurring between 1 and 2 years from diagnosis (n=1332) to 0.86 at 5 years (n=1067) and 1.38 (n = 429) at 10 years.  For each of the 12 SDI organ-based systems there was a steady accumulation of damage over time (figure 1).  By year 5 the highest incidence rates of damage were seen within the musculoskeletal group and the ‘other’ group.  When items were grouped based on their likely association with GC use, the cumulative incidence of items thought to have definite, probable/possible and no association with GC were 0.097, 0.053 & 0.203 respectively by 5 years and 0.207, 0.092 and 0.411 respectively by 10 years (figure 2). By 10 years, 42.6% of all damage was potentially related to GC use. 

Conclusion: In this inception cohort, the damage accumulated over time in a linear manner, whether damage items are grouped as a total SDI, according to organ-systems or when grouped according to their likely association with steroids.  A significant proportion of all damage accrued (42.6%) is related to steroid use and better therapeutic strategies to reduce steroid exposure are needed to improve long-term outcomes in SLE.