Risk of chronic kidney disease in 260 patients with lupus nephritis: analysis of a nationwide multicentre cohort with up to 35 years of follow-up

Objectives To compare proliferative (PLN) and membranous (MLN) lupus nephritis (LN) regarding clinical and laboratory presentation and long-term outcomes, and to investigate predictors of progression to chronic kidney disease (CKD). Methods Multicentre observational study, with retrospective analysis of a prospective cohort, using data from the Rheumatic Diseases Portuguese Registry - Reuma.pt. Patients with biopsy-proven PLN, MLN and mixed LN were included. Cox regression survival analysis was used to investigate predictors of CKD. Results A total of 260 patients were included. Median follow-up was 8 years (IQR 11; minimum 1, maximum 35 years). MLN patients presented with significantly lower serum creatinine [0.70 (IQR 0.20; minimum 0.50, maximum 1.30) mg/dl vs 0.80 (IQR 0.31; minimum 0.26, maximum 2.60) in PLN, P = 0.003]. Proteinuria levels did not differ between groups (P = 0.641). Levels of complement were reduced in PLN but nearly normal in MLN patients, and there were fewer patients with positive anti-dsDNA antibodies in the MLN group (P < 0.001). One year after the beginning of treatment, 62% of the patients achieved EULAR/ERA-EDTA complete response, with a further 5% achieving partial response. Patients with lower proteinuria at diagnosis were more likely to achieve a complete renal response at one year; however, proteinuria at diagnosis or at one year did not predict long-term CKD. Estimated glomerular filtration rate (eGFR) <= 75 mL/min/1.73 m2 at one year was the strongest predictor of progression to CKD (HR 23 [95% CI 8-62], P < 0.001). Other possible predictors included the use of azathioprine for induction of remission, older age at diagnosis and male sex. Conclusion Proteinuria levels did not predict LN histologic class in our cohort. eGFR cutoff of 75 mL/min/1.73 m2 after one year of treatment was strongly predictive of progression to CKD.