Occurrence of microalbuminuria in young people with Type 1 diabetes: importance of age and diabetes duration

Abstract

Aims: To determine the occurrence of microalbuminuria in young people with Type 1 diabetes mellitus followed prospectively for 2 years and to relate the presence of persistent elevations in urinary albumin excretion (UAE) to age, diabetes duration, puberty and other factors.

Methods: During a 2 year period, random urine samples were obtained from 471 patients, aged 8-18 years (mean +/-sd 12.9 +/- 2.3 years) with Type 1 diabetes duration 5.6 +/- 3.0 years, as part of routine clinical care. Urine albumin and creatinine concentrations were measured in 1310 samples (median, 3 samples per patient) and the albumin:creatinine ratio was calculated (in micrograms albumin per milligram creatinine). Height, weight, blood pressure (BP), glycated haemoglobin (HbA(1c)), blood glucose monitoring frequency and Tanner staging were collected from patients' medical records.

Results: Twenty-three per cent of patients had one or more sample with elevated UAE (> or =20 microg/mg) and 9.3% had persistent elevations (> or =2 samples > or =20 microg/mg). Those with and without persistent microalbuminuria did not differ significantly in age, diabetes duration, z-score for body mass index, pubertal status or BP percentile. Ten per cent of children <13 years old and 9% of children > or =13 years old had persistent microalbuminuria. Persistent microalbuminuria was significantly associated with diabetes duration only in older children (duration 0.5-3 years, 4%; 4-6 years, 8%; > or =7 years, 14%; P = 0.02, trend test). Mean HbA(1c) over the 2 years was 8.7 +/- 1.2%. In a logistic regression model, mean HbA(1c) was the only significant predictor of persistent microalbuminuria (odds ratio 1.3, 95% confidence interval 1.0-1.6, P = 0.05).

Conclusions: Microalbuminuria in older children with Type 1 diabetes is likely to be clinically significant. In younger children, it may reflect functional, reversible renal changes. Longitudinal analysis is needed to confirm the probable transient nature of microalbuminuria in young patients with Type 1 diabetes.

FIGURE 1

Distribution of urinary albumin excretion values for all urine samples (n = 1310) collected during the 2 year period. The majority of urine albumin:creatinine values (51%) were ≤5 μg/mg. Only 14% of all values were above normal (≥20 μg/mg). (To convert from μg/mg to mg/mmol, divide by 8.84.)

FIGURE 2

Prevalence of persistent microalbuminuria according to age and Type 1 DM duration. For younger patients (aged 8–12 years), prevalence of persistent microalbuminuria did not differ by Type 1 DM duration group. For older patients (aged 13–18 years), there was a significant trend towards higher prevalence of persistent microalbuminuria with longer Type 1 DM duration (test for trend, P = 0.02). Black bars represent Type 1 DM duration ≤3 years; white bars, Type 1 DM duration 4–6 years; and grey bars, Type 1 DM duration ≥7 years.