Background Time to complete remission, subsequent flares and time on immunosuppressives after remission are major determinants of the progression to advanced chronic kidney disease (CKD) in lupus nephritis (LN). However, the impact of these factors on the rate of glomerular filtration rate (GFR) deterioration is not known. Our objective was to determine their impact on the estimated GFR in LN.
Methods Patients with LN based on biopsy or abnormal proteinuria (>0.5g/day) for two consecutive visits were retrieved from the Toronto Lupus Clinic database. Individuals with advanced CKD at baseline (eGFR&x2266;29ml/min/1.73m2) were excluded. All patients were followed for ≥ 5 years. The primary outcome was the annual eGFR decrease (slope). Remission: proteinuria<0.5g/24h, inactive urinary sediment, serum creatinine (SCR) &x2266;120% of baseline. Flare: abnormal proteinuria (>0.5g/day) or SCR increase from normal to abnormal or >120% of baseline after remission.
Results Of 418 eligible patients, 209 (50%) achieved remission within the first year, 102 (24.4%) within the 2nd/3rd years, 70 (16.7%) after 3 years and 37 (8.9%) never achieved remission. Regarding flares, 82 patients (19.6%) never flared, 75 (18%) had one flare and 261 (62.4%) had ≥2 flares. The total number of flares was 1159; 203 (17.5%) were characterized by an eGFR decrease of ≥10ml/min/1.73m2. The trajectory and annual slope of eGFR according to time to remission and number of flares is shown in the Figure.
Conclusions Complete remission after 3 years or no remission is associated with a significant eGFR decrease, while remission during the 2nd/3rd year from LN diagnosis is not associated with any significant eGFR decrease over time. Patients with one flare did not have any significant impact on their renal function over time. Patients with ≥2 flares had a significant eGFR decrease over 20 years, after adjustment for other covariates. Time on immunosuppressives after complete remission is protective against eGFR decline.
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