Protein and albumin-to-creatinine ratios in random urines accurately predict 24 h protein and albumin loss in patients with kidney disease

Background: Random urine protein-to-creatinine (PCR) and albumin-to-creatinine (ACR) ratios have been proposed as alternatives to 24 In urine measurements to simplify sample collection and overcome errors. The aim of this study was to examine the ability of PCR and ACR to predict urinary 24 In protein and albumin loss, respectively, in patients with kidney disease, and determine the most appropriate time of collection. Methods: Eighty-three patients were recruited from a renal outpatient clinic. In a 24 In period, each collected an early-morning urine (EMU), second and third voids, and the remaining urine passed that day. PCR and ACR were determined in random urines and compared with the 24 h loss of protein and albumin, respectively. Results: For all patients, median (range) 24 h urine protein and albumin losses were 220 (30-15600) and 60 (<8-10,557) mg, respectively. Ratios derived from each of three random urines correlated well with 24 h protein or albumin loss (Spearman's r(s) > 0.87, P < 0.0001). Receiver operator characteristic (ROC) curve analysis showed PCR accurately predicted both an abnormal 24 h urine protein >= 150 mg/24 h (areas under curves [AUC] 0.90-0.92) and significant proteinuria above 300 mg/24 In (AUC between 0.97 and 1.00). ACR accurately predicted both an abnormal 24 h urine albumin >= 30 mg/24 h (AUC 0.98 to 0.99) and frank albuminuria at >= 300 mg/24 h or >= 700 mg/24 h (AUC between 0.99 and 1.00). EMU and random urines performed equally well in predicting proteinuria and albuminuria. from PCR and ACR, respectively. Conclusions: By careful choice of cut-offs, both PCR and ACR can be used in patients with kidney disease to rule in or rule out abnormal 24 In losses of protein and albumin. EMU and, importantly, random samples can be used as surrogates for 24 h urine collections.