Avaliação da variação temporal da taxa de filtração glomerular (ΔTFG) como marcador de resposta à terapia da nefrite lúpica: um estudo retrospectivo

Abstract

Lupus nephritis (LN), is present in 50-70% of patients with systemic lupus erythematosus (SLE), and is related with poor prognosis. In spite of treatment advances, 60% of the subjects may eventually develop chronic kidney disease (CKD). The most common manifestations of LN include an active urinary sediment, proteinuria and a decrease in glomerular filtration rate (GFR). They are also the main tools to determine treatment response, usually in a static way. We are not aware of any study that examined the predictive value of the slope changes in renal function over time. This study uses the delta glomerular filtration rate (ΔGFR) to evaluate patients with LN, and identifies factors related to loss or gain in renal function. Two hundred and twenty seven subjects with LN were analized among 660 patients with SLE whom were followed-up at our institution, between August of 2014 and June of 2016. Estimated GFR by CKD-EPI equation was evaluated longitudinally by linear regression and slopes calculated as ΔGFR in ml/min/month. Patients were grouped in tertiles of ΔGFR Each tercile was analyzed by social-demographic, clinical, laboratorial and histopathologic features. Results were compared to the treatment response variables, as established in the literature. CKD and time to end stage renal disease (ESRD) were analyzed as secondary outcomes. Women comprised 87% of the patients and mean age was 30 years. Proliferative LN predominated (77%) and mean of proteinuria at presentation was 3,6g/24h. The lower ΔGFR tertile (worst response) was independently associated with race (Afro-Brazilians, p=0.05), lower education level (p<0.001) and with proliferative LN (p=0.03). Patients in this tertile also had more flares (p<0.001) but less active urinary sediment (p=0.01). On the other hand, the upper tertile (better response) was associated with higher education (p<0.001), lower number off lares (p<0.001) and higher serum creatinine in the acute phase (p<0.001). Subjects in the lower tertile and those that did not achieve complete response were more likely to present CKD and end-stage renal disease (ESRD). The combination of traditional response variables with slope changes in GFR may provide an added discriminatory predictive value for evaluation of the treatment response in lupus nephrtitis.