Comparison of Associations of Urine Protein-Creatinine Ratio Versus Albumin-Creatinine Ratio With Complications of CKD: A Cross-sectional Analysis

Background: Urine albumin-creatinine ratio (ACR) and protein-creatinine ratio (PCR) are important markers of kidney damage and are used for prognosis in persons with chronic kidney disease (CKD). Despite how commonly these measurements are done in clinical practice, relatively few studies have directly compared the performance of these 2 measures with regard to associations with clinical outcomes, which may inform clinicians about which measure of urinary protein excretion is best. We studied the association of ACR and PCR with common complications of CKD. Study Design: Cross-sectional study. Setting & Participants: 3,481 participants with CKD in the Chronic Renal Insufficiency Cohort (CRIC) Study. Predictors: ACR and PCR. Outcomes: We examined the association between ACR and PCR with measures of common CKD complications: serum hemoglobin, bicarbonate, parathyroid hormone, phosphorus, potassium, and albumin. Measurements: Restricted cubic spline analyses adjusted for estimated glomerular filtration rate (eGFR; calculated by the MDRD [Modification of Diet in Renal Disease] Study equation) were performed to study the continuous association with our predictors with each outcome. Results: Mean eGFR was 43 6 13 (SD) mL/min/1.73 m(2) and median values for PCR and ACR were 140 and 46 mg/g, respectively. In continuous analyses adjusted for eGFR, higher ACRs and PCRs were similar and both were associated with lower serum hemoglobin, bicarbonate, and albumin levels and higher parathyroid hormone, phosphorus, and potassium levels. Across all outcomes, the associations of ACR and PCR were similar, with only small absolute differences in the outcome measure. Similar associations were seen in patients with diabetes mellitus. Limitations: Participants largely had moderate CKD with low values for ACR and PCR, so results may not be generalizable to all CKD populations. Conclusions: In persons with CKD, ACR and PCR are relatively similar in their associations with common complications of CKD. Thus, routine measurement of PCR may provide similar information as ACR in managing immediate complications of CKD. (C) 2013 by the National Kidney Foundation, Inc.