Estimated Albumin Excretion Rate Versus Urine Albumin-Creatinine Ratio for the Assessment of Albuminuria: A Diagnostic Test Study From the Prevention of Renal and Vascular Endstage Disease (PREVEND) Study

Abstract

Albumin-creatinine ratio (ACR) in spot urine samples is recommended for albuminuria screening instead of measured albumin excretion rate (mAER) in 24-hour urine collections. In patients with extremes of muscle mass, differences in spot urine creatinine values may lead to under- or overestimation of mAER by ACR. We hypothesized that calculating estimated AER (eAER) using spot ACR and estimated creatinine excretion rate (eCER) may improve albuminuria assessment. Diagnostic test study. 2,711 community-living individuals from the general population of the Netherlands participating in the PREVEND (Prevention of Renal and Vascular Endstage Disease) Study. eAER was computed as the product of ACR and eCER. eCER was computed using 3 previously validated methods (Ix, Ellam, and Walser). mAER, based on two 24-hour urine collections. Accuracy of the eAER and ACR were defined as the percentage of participants falling within 30% (P30) of mAER. Mean age was 49 years, 46% were men, mean estimated glomerular filtration rate was 84 ± 15 mL/min/1.73 m(2), and median mAER was 7.2 (IQR, 5.4-11.0) mg/d. Mean measured CER was 1,381 mg/d, and median ACR was 4.9 mg/g. Using the Ix equation, median eAER was 6.4 mg/d. In the full cohort, eAER was more accurate and less biased compared to ACR (P30, 48.9% vs 33.6%; bias, -34.2% vs -14.1%, respectively). In subgroup analysis, improvement was most notable in the middle and highest weight tertiles and in men. Using the other methods for eCER produced similar results. Little ethnic heterogeneity and a generally healthy cohort make extension of findings to other races and the chronically ill uncertain. In a large community-dwelling cohort, eAER was more accurate than ACR in assessing albuminuria.