VALIDATION DATA

This index records disease manifestations occurring within the 10 days preceding assessment.

The reliability of the SLEDAI 2K was demonstrated in a multicenter and multiethnic study of 93 patients with SLE, with an agreement for each of the items between 81.7% and 100%.

SLEDAI-2K has been validated for a 30-day window, in one hundred forty nine consecutive lupus patients that were seen over 9 weeks at the University of Toronto Lupus Clinic. In all but one patient, there was agreement between the SLEDAI-2K 10 and 30 days. Thus SLEDAI-2K 30 days is similar to SLEDAI-2K 10 days, both in patients in remission and with a spectrum of disease activity levels.  Touma Z, Urowitz MB, Gladman DD. SLEDAI-2K for a 30-day window. Lupus 2010;19:49-50.

To assess its reliability among less experienced clinicians, a reliability study with 3 rheumatology trainees and 9 patients with SLE according to a Latin square design was conducted. SLEDAI easily distinguished between patients (p = 0.0009), and physician variability was not statistically significant (p = 0.27). Intra observer agreement was 98.0 %. Hawker G et al. A Reliability Study of SLEDAI: A Disease Activity Index for Systemic Lupus Erythematosus (SLE). J Rheumatol 1993;20:657-660.

In the same study comparing rheumatology trainees and patients with SLE according to a Latin square design, interobserver reliability was 78.7%. 

In another study, ten patients with SLE, representing a spectrum of damage and activity, were included. Each patient was examined by 6 of 10 physicians from 5 countries. Analysis of variance for the SLEDAI revealed that it was able to detect differences among patients (P < 0.001), while no observer or order effects were detected in physicians and patients (P = 0.467 and P = 0.498, respectively). Gladman DD, et al. The reliability of the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index in patients with systemic lupus erythematosus. Arthritis Rheum. 1997 May;40(5):809-13. 0.

For the SLEDAI, a panel identified 24 variables as important factors in a disease activity index. These were used to generate 574 patient profiles, which were rated on a disease activity scale of 0-10 by 14 rheumatologists. A second rating of 10 of the profiles yielded scores that were not significantly different from the first, indicating that experienced clinicians can reliably make global estimates of disease activity. 

Multiple regression models were used to estimate the relative importance of the 24 clinical variables in the physicians' global rating of disease activity. These were estimated on a "training set" of 75% of physicians' ratings, and then validated on a "testing set," consisting of the remaining 25% of physicians' ratings. The explanatory power of the models in the training set was high (R2 = 0.93). The models' regression coefficients for the organ systems were simplified for easier use in clinical practice. This generated a "weighted" index of 9 organ systems for disease activity in SLE, the SLEDAI, as follows: 8 for central nervous system and vascular, 4 for renal and musculoskeletal, 2 for serosal, dermal, immunologic, and 1 for constitutional and hematologic.