Background/Purpose: Treat to target strategies are becoming the best approach for several rheumatic disorders. Recently retrospective analyses of two important lupus trials have reported that proteinuria is the single best predictor of renal outcome in lupus patients. Samples from these trials were however mainly Caucasians and mostly from patients in the first nephritis episode with non-severe renal involvement at entry. In addition, on average, adherence to intervention protocols is higher in clinical trials than in non-research settings. The purpose of this study was therefore to determine in real-life situation if proteinuria was also a good predictor of renal outcome in a geographical region with more racial diversity.

Methods: 94 biopsy-proven lupus nephritis patients with at least 7 years longitudinal follow-up at the Rheumatology Division of a tertiary university hospital were consecutively selected. Data were obtained using a standardized electronic database protocol including demographic data, clinical and laboratorial findings and treatment. Proteinuria, serum creatinine (SCr), urine red blood casts (RBC) and anti-dsDNA antibody were evaluated at baseline and after 3, 6, 12 months and then 7 years of follow-up. We assessed the ability of these biomarkers at these different time points to predict good long term renal outcome (defined as SCr<1.5mg/dl) at 7 years. Receiver operating characteristic (ROC) curves were generated to assess parameter cutoff and performance at these time points and to select the best parameter considering sensitivity, specificity, positive and negative predictive values. Kaplan Meier curves were used to assess renal survival of each group.

Results: 80 (85.1%) were women, 38 (40.4%) were non-white patients and 38 (40%) were not in the first episode of nephritis. At baseline, patients had mean SCr of 1.73±1.34 mg/dl, proteinuria 5.46±4.51g/24h, albumin 2.45±0.78g/dl and SLEDAI 9.46±4.23. Proteinuria <0.83g/24h at 12 months of follow-up was the best single predictor of good long-term renal outcome (Sensitivity=90.3%, Specificity=78.3%, PPV=62.0% e NPV=90.3% AUC=0.86, p<0.001). The addition of other variables to proteinuria analysis such as SCr and RBC at month 12 did not improve the predictive performance of this parameter. Further evaluation of the proposed proteinuria cut-off (<0.83g/24h at 12 months) revealed that this parameter is a good predictor of 7 years renal survival (defined as years free of dialysis) for pure membranous (p=0.005), proliferative nephritis (p=0.043), blacks (p=0.002), whites (p=0.001), anti-dsDNA positive (p=0.001), males (p=0.028) and females (p=0.003) patients.

Conclusion: We demonstrated in a real-life situation that proteinuria at 12 months of follow-up was the single best predictor of good renal outcome at 7 years for an ethnically diverse group. We further validated this parameter as long-term predictor of renal outcome for distinct histological classes, races, gender and anti-dsDNA profile.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/early-proteinuria-response-in-real-life-situation-predicts-long-term-lupus-renal-outcome-in-ethnically-diverse-group-with-biopsy-proven-nephritis/