Prevalence and risk factors for microalbuminuria in children and adolescents with type 1 diabetes: long-term experience of a single centre

Objectives: Diabetic nephropathy is a late complication of type 1 diabetes mellitus (T1DM) and microalbuminuria (MA) is an early and reversible sign of diabetic renal disease. Aims of this longitudinal study were: to define the prevalence of MA in children and adolescents with T1DM; to identify which risk factors are predictive for the development of MA. Methods: Seventy children and adolescents with T1DM [57% male; age at T1DM onset (T0) 5.95 3.16 yrs] were enrolled. The mean follow-up (FU) period was 7.18 1.89 yrs. Blood and urinary tests were performed once a year from the T0. MA screening was evaluated by urinary albumin concentration (UAC) or by timed urine collections for urinary albumin/creatinine ratio (ACR). MA was considered persistent (PMA) when at least 2 out of 3 consecutive evaluation of UAC and/or ACR were found positive. Results: PMA was found in 13% of patients. Subjects with PMA compared to normoalbuminuric ones had both significantly higher GFR at T0 (p = 0.025) and UAC at 1-year FU (T1) (p = 0.045). Predictive cut-off values for PMA development were 160 ml/min/1.73 m2 for GFR at T0 (sensitivity: 57%, specificity: 75%) and 8.5 mg/L for UAC at T1 (sensitivity:75%, specificity:80%). Relative risk for PMA was 23-times higher when UAC was >8.5 mg/L (p = 0.004). Kaplan- Meier survival curves as a function of age at T0 showed an increased probability of developing PMA among children in which T1DM onset occured between 5 and 11 years of age compared to those with younger onset (p = 0.014) and a pubertal diabetes duration >5 years was also a significant risk factor for PMA (p < 0.0005). Conclusions: Age at T1DM onset, pubertal timing, high UAC, and hyperfiltration predispose to PMA development and increase the risk for diabetic nephropathy. Specific cut-off values at T1DM onset and during first years of FU could provide indications to avoid disease progression.