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

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). 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. 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). Three years is the minimum duration of sCR protecting against development of IKF and damage accrual in patients with LN.