Proteinuria and serum creatinine after 12 months of treatment for lupus nephritis as predictors of long-term renal outcome: a case-control study.

Background: Lupus nephritis (LN) is a major source of morbidity and mortality in patients with systemic lupus erythematosus (SLE), with 10-25% of patients progressing to end-stage renal disease (ESRD).

Objective: This study aims to elucidate the predictive capabilities of 24-h proteinuria (24PTU) and serum creatinine (sCr) after 12 months of treatment with respect to long-term renal outcomes in LN in a single-center cohort of LN patients.

Methods: A retrospective analysis was performed on 214 patients diagnosed with LN followed in our center. Values of 24PTU and sCr were assessed at baseline and after 3, 6 and 12 months, and after 5 years and/or the last evaluation. Chronic kidney disease (CKD) was defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m for 3 months or longer. End-stage renal disease (ESRD) was defined as the need for permanent dialysis. Receiver operating characteristics curves (ROC) were used to test the best cut-off value of 24PTU and sCr at 12 months who predict bad long-term renal outcomes.  RESULTS: The mean follow-up period was 11.2 ± 7.2 years. The best cut-off values for 24PTU and sCr as predictor of CKD were, respectively, 0.9 g/24 h and 0.9 mg/dL. ROC curve for 24PTU had a slightly lower performance than ROC curve for sCr as predictor for CKD (PTU AUC = 0.68; sCr AUC = 0.70), but sensitivity and specificity were better for 24PTU (24PTU: sensitivity = 63.5%, specificity = 71.2%; sCr: sensitivity = 54.8%, specificity = 75.3%). When the outcome was ESRD the best cut-off points were 0.9 g/24hs and 1.3 mg/dL for 24PTU and sCr, respectively, and the curve performance was better for 24PTU (PTU AUC = 0.72; sCr AUC = 0.61).

Conclusions: In this ethnically diverse population with LN followed for a long time (> 10 years), levels of 24PTU > 0.9/day at 12 months was a good predictor of bad long-term renal outcome. The serum creatinine > 0.9 mg/dL and > 1.3 mg/dL at 12 months were also good predictors of CKD and ESRD, respectively. Patients with 24PTU < 0.9 g/day and sCr < 1.3 mg/dL at 12 months are not likely to develop ESRD because of the high negative predictive values (NPV) (93.2% and 82%). 24PTU and sCr are relevant as components for a treat-to-target strategy for LN treatment, since their high NPV corroborates their importance as good predictors of long-term renal outcome.