Albuminuria, Proteinuria, and Renal Disease Progression in Children with CKD.

BACKGROUND AND OBJECTIVES: The role of albuminuria as an indicator of progression has not been investigated in children with CKD in the absence of diabetes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Children were enrolled from 49 centers of the CKD in Children study between January of 2005 and March of 2014. Cross-sectional multivariable linear regression ( n =647) was used to examine the relationship between urine protein-to-creatinine (UP/C [milligrams per milligram]) and albumin-to-creatinine (ACR [milligrams per gram]) with eGFR (milliliters per minute per 1.73 m2 ). Parametric time-to-event analysis ( n =751) was used to assess the association of UP/C, ACR, and urine nonalbumin-to-creatinine (Unon-alb/cr [milligrams per gram]) on the time to the composite endpoint of initiation of RRT or 50% decline in eGFR.

RESULTS: The median follow-up time was 3.4 years and 202 individuals experienced the event. Participants with a UP/C≥0.2 mg/mg and ACR≥30 mg/g had a mean eGFR that was 16 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. Individuals with ACR<30 mg/g, but a UP/C≥0.2 mg/mg, had a mean eGFR that was 9.3 ml/min per 1.73 m2 lower than those with a UP/C<0.2 mg/mg and ACR<30 mg/g. When categories of ACR and Unon-alb/cr were created on the basis of clinically meaningful cutoff values of UP/C with the same sample sizes for comparison, the relative times (RTs) to the composite end-point were almost identical when comparing the middle (RT=0.31 for UP/C [0.2-2.0 mg/mg], RT=0.38 for ACR [56-1333 mg/g], RT=0.31 for Unon-alb/cr [118-715 mg/g]) and the highest (RT=0.08 for UP/C [>2.0 mg/mg], RT=0.09 for ACR [>1333 mg/g], RT=0.07 for Unon-alb/cr [>715 mg/g]) levels to the lowest levels. A similar trend was seen when categories were created on the basis of clinically meaningful cutoff values of ACR (<30, 30-300, >300 mg/g).

CONCLUSIONS: In children with CKD without diabetes, the utility of an initial UP/C, ACR, and Unon-alb/cr for characterizing progression is similar.