|The following article is part of conference coverage from the European League Against Rheumatism (EULAR) Congress 2018 in Amsterdam, The Netherlands. Rheumatology Advisor’s staff will be reporting breaking news associated with research conducted by leading experts in rheumatology. Check back for the latest news from EULAR 2018.|
Compared with the Systemic Lupus Erythematosus (SLE) Disease Activity Index 2K (SLEDAI-2K), the SLE Disease Activity Score (SLE-DAS) demonstrated superior detection of SLE activity changes while maintaining strong validity, according to findings presented at the European League Against Rheumatism (EULAR) Congress 2018, held in Amsterdam, June 13 to 16, 2018.
The SLEDAI is commonly used to assess SLE disease activity, however, its ability to discern worsening or improvement is poor because of its categoric scoring system and because it does not include hemolytic anemia and other relevant facets of SLE. Investigators were interested in deriving and validating a scoring system that retained the simplicity and high specificity of the SLEDAI while improving its sensitivity to change.
A total of 324 patients with SLE were followed at a tertiary lupus clinic between 2014 and 2017, with pertinent laboratory and clinical data — including disease activity as scored by the Physician Global Assessment (PGA; 0-3 scale) and SLEDAI-2K — recorded at each visit. The PGA, considered the gold standard dependent variable, independent variables including SLEDAI-2K items and multiple continuous factors (proteinuria, white blood cell and platelet counts, swollen joint counts), and non-SLEDAI-2K items (hemolytic anemia, cardiopulmonary and gastrointestinal involvement), were analyzed using multivariable regression models for the derivation of the SLE-DAS.
At the final outpatient visit, Spearman correlations were calculated among the PGA, SLEDAI-2K, and SLE-DAS, to evaluate validity. Using a PGA change ≥0.3 as an indicator of significant improvement or worsening, SLEDAI-2K (change ≥4) was compared with SLE-DAS using receiver operating characteristic curve analysis and by examining the area under the curve (AUC).
There were 17 total items included in the final model for the SLE-DAS, which exhibited high PGA and SLEDAI-2K correlations (rho=0.975; P <.0005; and rho=0.94; P <.0005; respectively). When considering changes vs PGA improvement ≥0.3, the AUC for the SLE-DAS (AUC=0.927, 95% CI, 0.885-0.969; P <.0005) showed considerably better performance than that for SLEDAI-2K (AUC=0.787; 95% CI, 0.718-0.857; P <.0005). For PGA worsening ≥0.3, the SLE-DAS (AUC=0.994; 95% CI, 0.988-1.000; P <.0005) again outperformed the SLEDAI-2K (AUC=0.914; 95% CI, 0.870-0.959; P <.0005). Based on these results, the researchers set a cut-off for PGA elevation/reduction of an SLE-DAS change ≥1.72.
For improvement or worsening of PGA ≥0.3, the SLE-DAS had a sensitivity of 82.1/93.1, a specificity of 96.9/97.7, a positive predictive value of 87.3/90.0, and a negative predictive value of 95.4/98.5. In comparison, the SLEDAI-2K demonstrated a sensitivity of 44.8/46.6, a specificity of 96.5/99.6, a positive predictive value of 76.9/96.4, and a negative predictive value of 87.0/89.5.
“The SLE-DAS presents good construct validity and much higher discriminative power to detect changes in SLE disease activity as compared to SLEDAI-2K,” concluded the authors, adding, “External validation in another SLE cohort is underway.”
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Jesus D, Matos A, Henriques C, et al. Detection of changes in SLE disease activity is highly improved with SLE-DAS as compared to SLEDAI: derivation and preliminary validation of the SLE Disease Activity Score (SLE-DAS). Presented at: European League Against Rheumatism (EULAR) Congress 2018; June 13-16, 2018; Amsterdam, The Netherlands. Abstract FRI0641.