Can we identify adolescents at high risk for nephropathy before the development of microalbuminuria?

AIMS: To determine whether higher than average albumin excretion during early puberty identifies subjects who will subsequently develop microalbuminuria (MA) and clinical proteinuria. METHODS: Longitudinal data from the Oxford Regional Prospective Study of Childhood Diabetes (ORPS; n = 554, median duration of follow-up 10 years; range 3.0-16.7) with assessment of albumin/creatinine ratios in three early morning urine samples collected annually. An albumin excretion phenotype was derived from longitudinal data, for each individual, defining deviation from the mean of regression models, including covariates gender, age, duration of diabetes and age at assessment. Tracking of the phenotypes was confirmed in a second independent cohort from Perth, Australia. RESULTS: The albumin excretion phenotype showed reasonable correlation between age 11-15 years and age 16-18 years in both cohorts, indicative of good 'tracking'. In the ORPS cohort, tertiles of the albumin excretion phenotype at aged 11-15 years were predictive of subsequent risk for the development of MA. All of the subjects developing clinical proteinuria had an albumin excretion phenotype in the upper tertile or an HbA(1c) > 9% at aged 11-15 years. CONCLUSIONS: Identification of adolescents at risk of diabetic nephropathy using an albumin excretion phenotype is feasible. When combined with elevated HbA(1c), it may identify subjects for trial of early intervention with angiotensin-converting enzyme inhibitors/angiotensin-II receptor antagonists and statins to improve long-term prognosis in these subjects where sustained improvement in glycaemic control may be difficult to achieve.