#5769 Measuring Proteinuria at 12 Months in Lupus Nephritis: A Useful Tool?

Abstract

Background and Aims Lupus nephritis is a well know manifestation of systemic lupus erythematosus (SLE) and it can progress to end stage kidney disease (ESKD) in 10-30% of patients [1]. Several studies have been conducted to find out whether proteinuria detected earlier in the course of lupus nephritis is associated with worse kidney related outcomes, such as progression to chronic kidney disease [2]. Method We retrospectively reviewed a cohort of 67 patients referenced to our center with the diagnosis of lupus nephritis until 2019. We evaluated proteinuria (g/g) in a random urine sample measured 12 months after diagnosis and beginning of treatment of lupus nephritis and divided patients into two groups: those with proteinuria less than or equal to 0.3 g/g– group 1(n = 11; 35%) and those with proteinuria superior to 0.3 g/g– group 2 (n = 20; 65%) that had measures of our variables of interest. These groups were compared regarding a continuous variable: serum creatinine measured in the 7th year of follow up, as evaluated in previous studies [3]. We compared the median of serum creatinine values between group 1 and group 2 using Mann-Whitney test, due to the absence of normal distribution of serum creatinine. We also compared the median of serum creatinine in the 7th year to proteinuria measured at 3 and 6 months. Results Mean follow up was 13.36 ± 7.8 years and 81.7% (n = 57) were women, with a median age of 33.0 ±12.85 years. A total of 8 patients (11.9%) progressed to ESKD defined by the need for renal replacement therapy or being submitted to renal transplantation. Only 1 patient died due to a nosocomial infection. We had a sample of 31 patients, 26 women and 5 men (p = 0.591) (missing n = 36). Baseline median serum creatinine in group 1 was 0,95 mg/dl and in group 2 was 0.78 mg/dl (p = 0.086). We obtained a median serum creatinine of 0.69 mg/dl (Interquartile range (IQR): 0.61-0.87) in group 1 versus0.92 mg/dl (IQR: 0.66-1.25) in group 2 (p = 0.04). Medians of serum creatinine in the 7th year regarding proteinuria measured at 3 and 6 months were not significantly different (p>0.05). Conclusion In our cohort, the group with a higher persistent proteinuria (> 0.3 g/g), one year after lupus nephritis diagnosis, had a significantly higher serum creatinine (7 years after diagnosis). Although previous studies have shown that reducing proteinuria to less than 0.5–0.8g/d 3 by 1 year of treatment predicts good long-term kidney outcomes, our particular data suggest that further reducing to less than 0.3 g/g may provide additional benefit in the long run [2], even though, due to our reduced sample, more investigation is required. From the above mentioned, one may consider 12 months proteinuria as a potential predictor to long-term renal outcomes with lupus nephritis. More studies are necessary to validate this hypothesis.