Objective: The Lupus Foundation of America Rapid Evaluation of Activity in Lupus (LFA-REAL) clinician-reported outcome (ClinRO) and the LFA-REAL patient-reported outcome (PRO) were developed in order to capture manifestations of SLE from the perspective of both the clinician and the patient. The aim of this study is to compare the LFA-REAL ClinRO and PRO with other lupus disease activity measures. Methods A cross-sectional analysis of patients from a single-centre cohort was performed using Spearman's correlation. Disease activity measures included were LFA-REAL ClinRO (range 0-1400), LFA-REAL PRO (range 0-1200), Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K), clinical SLEDAI-2K and Physician Global Assessment (PGA, range 0-100). Results Two hundred and twenty-seven patients with SLE were studied. The mean age was 46.3 (SD: 13.8); 212 (93.4%) were female. The mean (SD) LFA-REAL ClinRO was 25.4 (34.7), LFA-REAL PRO was 241.1 (187.6), PGA was 11.9 (15.4), SLEDAI-2K was 2.3 (3.3) and clinical SLEDAI-2K was 1.6 (2.9). The LFA-REAL ClinRO correlated with PGA (r=0.758, p<0.001), SLEDAI-2K (r=0.608, p<0.001) and clinical SLEDAI-2K (r=0.697, p<0.001); the LFA-REAL PRO correlated modestly with PGA (r=0.160, p=0.016), SLEDAI-2K (r=0.121, p=0.069), clinical SLEDAI-2K (r=0.143, p=0.031) and LFA-REAL ClinRO (r=0.161, p=0.015). Conclusions The LFA-REAL ClinRO and the LFA-REAL PRO had good and weak correlations, respectively, with several physician-based disease activity measures in a cross-sectional study, suggesting their potential usefulness in establishing disease severity. Longitudinal studies will be required to determine their value in monitoring patients with SLE.