How to measure and monitor albuminuria in healthy toddlers

Objective Urinary albumin:creatinine ratio (U-ACR) in first morning void (FMV) urine samples collected over three days is the recommended method for measuring and monitoring albuminuria in adults in the clinical setting. Such a guideline is not available for toddlers and young children. We tested several urine collection strategies for albuminuria measurement in toddlers in a prospective observational study. Main outcomes measures Both a FMV and a random daytime urine sample were collected on three consecutive days at week 0, 4, and 8 in toddlers aged 12-48 months. Intra-individual coefficients of variation (CV) of urinary albumin (U-AC) and U-ACR were compared using only the first measurement and using all three measurements per time point. In addition, these were compared with published CV of adults. Results A total of 80 toddlers (mean age 26.6 months, 53% male) were included. Intra-individual CV of FMV samples appeared lower than with random samples. The intra-individual CV in U-AC or U-ACR was smaller using multiple compared to single samples. The lowest intra-individual CV was observed when U-AC was measured in FMV over three consecutive days (38.3%). CV of U-AC was similar to values published for adults. However, U-ACR CV was considerably higher in toddlers. Conclusions These data show that-in analogy with adult data-multiple first morning void urine samples should be preferred to single or random urine samples for establishing and monitoring albuminuria in toddlers. Further studies are needed to investigate why creatinine correction for differences in urine dilution is less effective in children.