Background/Purpose: The SIMPLE (SIMple Disease Assessment for People with Lupus Erythematosus) index is a composite numeric tool that captures disease activity from patients’ self-assessment with minimal physicians’ input.  The SIMPLE index consists of 2 components: patient self-reported survey questionnaire (3 items from the lupus symptoms domain from the validated LupusPRO, 10 items from Lupus Impact Tracker [LIT], change in the health status and current glucocorticoids use [and dose]) and two laboratory tests (low complements [C3/C4] and urine protein-creatinine ratio >0.5).  The values are put in an equation to derive a number, which is transformed to a 0- to 100-point scale by a formula using weighted scores of the above parameters.  The SIMPLE index has been validated in US with good correlation with physicians’ assessment of disease activity.

Objective: To validate the SIMPLE index for systemic lupus erythematosus (SLE) disease activity assessment in Chinese patients.

Methods: Adult patients (age ≥18 years) who fulfilled the 2013 SLICC criteria for SLE and were followed in the Rheumatology clinics of Tuen Mun Hospital, Hong Kong were recruited in a cross-sectional study.  Participants were invited to complete the SIMPLE questionnaire before seeing doctors on the same day.  The two laboratory results were supplemented by research nurses.  Physicians, who were blinded to the SIMPLE results, were asked to complete disease activity assessment by the SELENA-SLEDAI and physicians’ global assessment (PGA) after consultation.  Correlation was made between the SIMPLE score and the SLEDAI/PGA scores by Spearman’s rank correlation test.  Receiver operating characteristic (ROC) analysis was performed to find the best cut-off SIMPLE score that predicted a clinical SLEDAI score of 1-6 (mild SLE activity) and ≥7 (moderate/severe activity).

Results: 364 SLE patients were studied (94% women; age 45.4±13.4 years; disease duration 13.2±8.0 years).  The proportion of patients having a history of neuropsychiatric and renal disease that required immunosuppressive therapies was 9.3% and 56%, respectively.  At the time of questionnaire completion, 69 (19%) patients had SLEDAI ≥6 and 192 (53%) had SLEDAI 1-5.  The mean SLEDAI was 3.04±2.85 and PGA score was 0.62±0.55.  A total of 161 (44%) had SDI score ≥1.  The mean SIMPLE index was 26.0±12.9.  SIMPLE index correlated significantly with SLEDAI (ρ=0.76; p< 0.001) and PGA score (ρ=0.48; p< 0.001).  ROC analysis showed that a SIMPLE index of >27 points best predicted a clinical SLEDAI score of 1-6 (area under the curve [AUC] 0.78[0.73-0.84]; sensitivity 0.75; specificity 0.71), and >36.8 points best predicted a clinical SLEDAI score of ≥7 (AUC 0.87[0.69-1.00]; sensitivity 0.88, specificity 0.85).

Conclusion: SIMPLE shows a good correlation with SELENA-SLEDAI and PGA.  It is a simple tool that enables patients to self-report disease activity and communicate with the health care team more efficiently.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/validation-of-the-simple-index-for-disease-activity-of-systemic-lupus-erythematosus-in-chinese-patients/