Article Text
Abstract
Objective Two recent important lupus nephritis trials reported that proteinuria was a good predictor of renal outcome in Caucasians, but data on real-life situation, other races and severe nephritis are lacking to substantiate this finding as a simple test to guide clinical practice. The aim of this study was to validate proteinuria as a predictor of long-term renal outcome in real-life situation in a racially diverse group of patients with severe nephritis.
Methods Proteinuria, serum creatinine (SCr) and urine red blood cells were assessed at baseline and after 3, 6 and 12 months, as early predictors of long-term renal outcome (SCr <1.5 mg/dL at 7 years), in 94 patients with biopsy-proven lupus nephritis. The parameter performance and cut-off values were computed by receiver operating characteristic curves. Kaplan-Meier curves were used to validate the parameter.
Results A proteinuria <0.8 g/24 hours at 12 months was the best single predictor of long-term renal outcome (sensitivity 90%, specificity 78%, positive predictive value 67%, negative predictive value (NPV) 94% and area under the curve 0.86; p<0.001). Addition of other variables to proteinuria such as SCr and haematuria at 12 months did not improve its performance. The proteinuria cut-off value of 0.8 g/24 hours at 12 months was a good predictor of 7-year renal survival (years free of dialysis) for patients with pure membranous (p=0.005) and proliferative nephritis (p=0.043), as well as black (p=0.002) and white race (p=0.001), anti-dsDNA positive (p=0.001) and anti-dsDNA negative (p=0.04) and male (p=0.028) and female (p=0.003) patients.
Conclusion We provided novel evidence that, in a real-life situation, proteinuria at 12 months of follow-up was the single best predictor of renal outcome at 7 years for an ethnically diverse group of patients with severe nephritis and a valid parameter for distinct histological classes, races, genders and anti-dsDNA profiles. The remarkably high NPV obtained reinforces its recommendation as the ideal predictor for clinical practice, since it is of low cost, easy to interpret, non-invasive and widely available.
- Lupus Nephritis
- Systemic Lupus Erythematosus
- Outcome research
- Proteinuria
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Footnotes
Contributors All authors equally contributed to this article and meet the authorship criteria.
Competing interests EFB and EB received a grant from Conselho Nacional de Desenvolvimento Científico e Tecnológico (#307226/2014-0 to EFB and #305068/2014-8 to EB) not related with this work.
Ethics approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement All data are provided in full in the results section of this paper.