Abstract
BACKGROUND: 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. STUDY DESIGN: Diagnostic test study. SETTING & PARTICIPANTS: 2,711 community-living individuals from the general population of the Netherlands participating in the PREVEND (Prevention of Renal and Vascular Endstage Disease) Study. INDEX TEST: eAER was computed as the product of ACR and eCER. eCER was computed using 3 previously validated methods (Ix, Ellam, and Walser). REFERENCE TEST: 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. RESULTS: 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. LIMITATIONS: Little ethnic heterogeneity and a generally healthy cohort make extension of findings to other races and the chronically ill uncertain. CONCLUSIONS: In a large community-dwelling cohort, eAER was more accurate than ACR in assessing albuminuria.