Canadian Rheumatology Association (CRA) Meeting, Quebec City, Quebec, February 3-6, 2010

Objective: A number of outcome measures to assess disease activity in SLE patients have been developed.SLEDAI-2K (Systemic Lupus Erythematosus Activity Index-2K) is a reliable valid, simple, one-page activity index recording features of active lupus as present or not present.Thus its utility in clinical trials is limited as it cannot reflect partial improvement in a disease manifestation.The objective of this study is to develop a SLEDAI-2K responder measure which could document a minimum 50% improvement in disease manifestations among lupus patients.Methods: Derivation of SRI-50 (SLEDAI-2K Responder Index-50) from SLEDAI-2K: A new definition for each of the original descriptors of SLEDAI-2K was created to reflect a minimum improvement of 50%.The definitions of descriptors of SRI-50 were constructed based on a literature review for each specific organ system.The new assigned scores for the descriptors of SRI-50 were derived by dividing the score of SLEDAI-2K by 2. Assessing the content validity of the draft instruments: SRI-50 form was assessed by expert rheumatologists reviewing the instruments and providing critical feedback.Results: Testing of SRI-50: One hundred patients who had experienced lupus flares or had persistently active disease were assessed initially and then reassessed after treatment was initiated.SLEDAI-2K was determined on the first visit and again at the second visit along with SRI-50.Results: SRI-50 and the data retrieval form to accurately document the clinical and laboratory findings of each descriptor were developed.Seventy two patients didn't change their SRI-50 because their manifestations resolved or didn't meet the definition of SRI-50 Twenty eight patients with varying levels of disease activity at the first visit (3 had SLEDAI-2K 2, 3 had 4; 6 had 6; 6 had 8; 3 had 10; 2 had 12; 1 had 16, 1 had 18; 2 had 20; 1 had 21) were further studied with SRI-50.SRI-50 was able to demonstrate incomplete (but ≥50%) improvement which would not have been discerned using SLEDAI-2K.Such incomplete improvement was demonstrated in 13 of the 24 SLEDAI-2K descriptors and in 6 of the 9 organ systems that were present in these patients.Conclusion: SLEDAI-2K Responder Index-50 is a promising instrument that can describe partial improvement in disease activity between visits in lupus patients.