Three years is the minimal effective duration of sustained clinical remission which prevents impaired kidney function and damage accrual in lupus nephritis

Objectives: To assess the minimum effective duration of remission preventing damage accrual (Systemic Lupus International Collaborating Clinics damage index [SDI]) and impaired kidney function (IKF: estimated glomerular filtration rate of <60 mL/min/1.73 m2 for at least 3 months) in active lupus nephritis (LN). Methods: Patients with biopsy-proven LN followed up at least twice yearly were enrolled; clinical variables were collected regularly. Sustained clinical remission (sCR) was defined as estimated glomerular filtration rate of >60 mL/min/1.73 m2, proteinuria of <0.5 g/24 h and clinical systemic lupus erythematosus disease activity index of 0 for at least 1 year. Log-linear regression and a time-dependent Cox proportional hazard model were used to assess the minimum duration of sCR capable of preventing SDI increase and IKF development. Results: In total, 293 patients with LN were included (median follow-up: 15.7 [10.4-22.9] years) of whom 84.3% achieved sCR lasting 8.7 (5.4-13.1) years. At last observation, the increase in SDI was higher in patients who never achieved sCR (median: 2 [1-2.5] vs 1 [0-1.5]; P <.001). A minimum duration of 3 years of sCR prevented SDI increase (% change = −41.1%; P =.003). The analysis on IKF involved only patients with the longest follow-up; 224 patients had ≥10 years of observation. Among them, 50 (22.3%) developed IKF. A minimum duration of 3 years of sCR prevented IKF (hazard ratio = 0.10; P <.001). IKF-free survival rate at 10, 20, and 25 years was 87%, 68%, and 40% for patients who never achieved sCR and 99%, 96%, and 91% for patients with at least 3 years of sCR, respectively (P <.001). Conclusions: Three years is the minimum duration of sCR protecting against development of IKF and damage accrual in patients with LN.