Measuring Disease Damage and Its Severity in Childhood-Onset Systemic Lupus Erythematosus

Abstract

Objective: To describe the frequency and types of disease damage occurring with childhood-onset systemic lupus erythematosus (SLE) as measured by the 41-item Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI), and to assess the SDI's ability to reflect damage severity.

Methods: Information for the SDI was prospectively collected from 1,048 childhood-onset SLE patients. For a subset of 559 patients, physician-rated damage severity measured by visual analog scale (MD VAS damage) was also available. Frequency of SDI items and the association between SDI summary scores and MD VAS damage were estimated. Finally, an international consensus conference, using nominal group technique, considered the SDI's capture of childhood-onset SLE-associated damage and its severity.

Results: After a mean disease duration of 3.8 years, 44.2% of patients (463 of 1,048) already had an SDI summary score >0 (maximum 14). The most common SDI items scored were proteinuria, scarring alopecia, and cognitive impairment. Although there was a moderately strong association between SDI summary scores and MD VAS damage (Spearman's r = 0.49, P < 0.0001) in patients with damage (SDI summary score >0), mixed-effects analysis showed that only 4 SDI items, each occurring in <2% of patients overall, were significantly associated with MD VAS damage. There was consensus among childhood-onset SLE experts that the SDI in its current form is inadequate for estimating the severity of childhood-onset SLE-associated damage.

Conclusion: Disease damage as measured by the SDI is common in childhood-onset SLE, even with relatively short disease durations. Given the shortcomings of the SDI, there is a need to develop new tools to estimate the impact of childhood-onset SLE-associated damage.

Figure 1.

Damage accumulation over time. A, The relation of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) summary scores and disease duration in the cohort (n = 1,048) is shown for patients up to 10 years since the diagnosis with childhood-onset SLE. Analysis of variance supports a strong linear relationship (R² = 0.9, P < 0.0001). B, The relationship of the presence of damage in the 9 organ domains of the SDI is shown for disease durations up to 6 years. Diabetes mellitus and malignancies were very rare and are omitted. Lines are moving averages of annual values. The most commonly damaged organ systems were the neuropsychiatric, musculoskeletal, renal, and skin. Malignancies and diabetes mellitus were present in <0.4% of the composite cohort, and both SDI organ systems are excluded from the figure. ** = function of linear trend line, including information about model fit (R²); GI = gastrointestinal; MSK = musculoskeletal.

Figure 2.

Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) summary scores and physician rating of perceived damage severity in childhood-onset SLE. A, The relationship between physician-rated severity of damage (MD-VAS_damage) and the SDI summary score in patients with childhood-onset SLE is shown, with a focus on MD VAS damage ratings of 0, 1, or 2, showing ratings of up to 2 (range 0–10). Despite SDI scores of 1 or 2, some physicians provided damage severity ratings of 0. Conversely, only 76% of patients with SDI summary scores of 0 received the best possible MD VAS damage rating. B, The relationship between physician-rated severity of damage (MD-VAS_damage) and the SDI summary score in patients with childhood-onset SLE is shown, with SDI scores up to 12. With higher SDI summary scores, more commonly higher MD VAS damage ratings are assigned.