Validation of SIMPLE Index for Lupus Disease Activity

An easy, quick tool requiring minimal training or health care provider input would potentially have greater uptake for clinical use among rheumatologists and primary care physicians for assessment of disease activity in systemic lupus erythematosus (SLE). SIMPLE (SIMple Disease Assessment for People with Lupus Erythematosus) index is a composite numeric tool that is easy and quick to calculate. We prospectively assessed the performance of the SIMPLE index as a disease activity surrogate against physician-based disease activity measures.

Ninety-nine consenting patients meeting American College of Rheumatology SLE classification criteria were recruited. Safety of Estrogen in Lupus National Assessment-Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI), physician global assessment, and SIMPLE index were obtained during routine visits. SIMPLE index is a 17-item patient-reported questionnaire that includes 2 laboratory tests. Health care provider input is needed only to provide laboratory results (normal/abnormal) and confirming patient-reported current use and dosing of glucocorticoids. We performed Spearman test to assess correlation of SIMPLE index with SELENA-SLEDAI and physician global assessment.

Mean age (SD) was 39.7 (12.3) years. The correlation coefficient between SIMPLE index and SELENA-SLEDAI was 0.56 (P = 0.0001), and that between SIMPLE index and physician global assessment was 0.54 (P = 0.0001). In SLE patients without fibromyalgia (FM), the correlation of SIMPLE index with SELENA-SLEDAI and physician global assessment was 0.58 (P = 0.0001) and 0.57 (P = 0.0001), respectively.

SIMPLE index is strongly correlated with formal physician assessments of disease activity in SLE, and correlation was marginally higher among those without FM. SIMPLE index can be performed easily in places with limited physician and laboratory resources.