Síndrome Nefrótica Idiopática na criança e no adolescente: evolução, fatores de risco e modelo de predição clínica para progressão da doença renal crônica

Abstract

The Idiopathic Nephrotic Syndrome (INS) is associated with high morbidity and represents is a major cause of Chronic Kidney Disease (CKD) in the pediatric population. Nevertheless, there are still limited data on risk factors related to the progression of CKD among patients with INS. In view of that, the present study aims to describe the clinical course of a cohort of children and adolescents with SNI, assisted in the Pediatric Nephrology Unit, Clinics Hospital, Federal University of Minas Gerais (UNP-HC-UFMG) in the period between 1970 and 2012 and also to develop a prognostic risk score for CKD using demographic, clinical and laboratory factors. In this study, 294 patients aged 0-18 years admitted to the program from 1970 to 2012 were included. The variables analyzed at the beginning and at the end of treatment were: sex, race, age of onset of symptoms, age at admission, age at last visit, blood pressure, weight, height and index of body weight. In addition, the following laboratory data were analyzed: hematuria, proteinuria in 24 hours urine, serum creatinine and histopathological diagnosis of SNI, whenever renal biopsy was performed. The use and effectiveness of the following immunosuppressants have been evaluated: corticosteroids, cyclophosphamide and cyclosporin A. The primary outcome was progression to CKD defined as a reduction in glomerular filtration rate below 60mL/min/1.73m2. Survival analysis was used to assess the time until the occurrence of the event of interest. A predictive model for the development of CKD was developed. For this, we used the model of failure rates and the Cox proportional statistical C. Finally, we developed a prognostic risk score, using each variable related to CKD. From the patients analyzed, 187 were male and 107 female. The median age at onset of symptoms was 3.1 years, the age at admission was 5.2 years and the follow-up time was 6.9 years. 38.4 % of patients had a diagnosis of FSGS on renal biopsy. At final follow-up, 30 patients (10.2 %) developed CKD. In multivariate analysis, we found three variables that maintained an independent association with the progression of INS to CKD: age of onset of symptoms (HR 1.17 , 95% CI = 1.07 to 1.28 , p < 0.001), hematuria (HR 3.30, 95% CI = 1.48 to 7.35 , p = 0.003) and resistance to corticosteroids (HR 3.15, 95% CI = 5.43 to 100.3 , p < 0.001). Thus, it was assigned a risk score for each of the 294 patients ranged from 0 to patients without risk factors and age at onset of symptoms less than 3 years, up to 13, for those patients with all risk factors and age at onset of symptoms above 12.1 years of age. Based on this score, the patients were stratified into three categories: low risk (0 to 1), medium risk (2 to 7) and high risk (8 to 13). The accuracy of the model was considered good by the c statistic, with an area under the curve of 0.92 (95% CI = 0.87-0.97) in 10 years. In summary, this study proposes a model to predict prognostic risk for CKD in children and adolescents with INS. Patients manifesting INS above 8 years of age who present with hematuria and with resistance to corticosteroid treatment have a poorer prognosis, with a high probability of developing CKD.