Background/Purpose:   In patients with active disease, physicians look for an early signal in response to treatment to guide their therapeutic decisions.

Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) measures disease activity in 24 descriptors, generates a total score describing disease activity overall. SLEDAI-2K records descriptors of disease activity as present or absent. In the SLEDAI-2K Responder Index 50 (S2K RI-50), each of the 24 descriptors has a definition for a ≥ 50% improvement resulting in an appropriate 50% score for the corresponding descriptor and a total score describing disease activity overall.

We aimed to determine if a signal of improvement in disease activity at 3 months predicts further improvement at 6 months.

Methods:   Consecutive active lupus patients who attended the clinic between 2012 and 2014 were screened for inclusion. Patients were included if they: 1) had at least 1 of the following 5 SLEDAI-2K clinical organ systems active (vascular, renal, musculoskeletal, serosal or skin); central nervous system was excluded and 2) started or increased prednisone therapy and/or immunosuppressants.  All patients had to have a follow-up visits at 3 and 6 months.

Outcome measures: Disease activity was measured by SLEDAI-2K at all visits and by S2K RI-50 at 3 months.

Study definitions: Signal of improvement by SLEDAI-2K is defined as a decrease by ≥1 in SLEDAI-2K score at 3 months. Signal of improvement by S2K RI-50 is defined as a decrease by ≥1 in S2K RI-50 score at 3 months.

Study endpoints:

Based on the change in the total SLEDAI-2K score (baseline – last visit), each of the patients at last visit were grouped as: 1) improved (SLEDAI-2K decreased by ≥4) and not improved (SLEDAI-2K decreased <4).

First, we identified the patients with SLEDAI-2K signal at 3 months and those who did not have a SLEDAI-2K signal were further evaluated for possible S2K RI-50 signal. Patients with signals were reevaluated at 6 months to determine if they had further improvement.

Results:   87 patients with mean SLEDAI-2K at baseline visit was 8.9±5.1 were studied.  90% were female, age at baseline visit was 40.0±12.4 and disease duration was 13.2±9.6years.

Signals of improvement: Of the 87 patients, 54 (62%) had a SLEDAI-2K signal at 3 months. Of the 33 patients who did not have a SLEDAI-2K signal, a S2K RI-50 signal was identified in 11 (33%) patients.

Study endpoints: Of the 54 patients with SLEDAI-2K signal at 3 months, 28 (52%) patients improved at 6 months. Of the 11 patients with S2K RI-50 signal at 3 months, 5 (46%) improved at 6 months.

Conclusion:   A signal of improvement at 3 months predicts further improvement in disease activity at 6 months. S2K RI-50 signal at 3 months, which is not discern by SLEDAI-2K, predicts improvement in half of the patients at 6 months. S2KRI-50 can identify non responders at 3 months who will respond at 6 months