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

This version was published on 1 November 2009

Ann Clin Biochem 2009;46:468-476
doi:10.1258/acb.2009.009001
© 2009 Association for Clinical Biochemistry

 

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Original Articles


Mark Guy1,
Joanna K Borzomato1,5,
Ronald G Newall2,
Philip A Kalra3 and
Christopher P Price4


1 Department of Clinical Biochemistry, Salford Royal NHS Foundation Trust, Hope Hospital, Salford;
2 Highover Park, Amersham, Bucks;
3 Department of Renal Medicine, Salford Royal NHS Foundation Trust, Salford;
4 Department of Clinical Biochemistry, University of Oxford, Oxford, UK;
5 Present address: Department of Clinical Biochemistry, Royal Albert Edward Infirmary, Wigan, UK


Corresponding author: Mark Guy. Email: mark.guy{at}srft.nhs.uk


Background: Random urine protein-to-creatinine (PCR) and albumin-to-creatinine(ACR) ratios have been proposed as alternatives to 24 h urinemeasurements to simplify sample collection and overcome errors.The aim of this study was to examine the ability of PCR andACR to predict urinary 24 h protein and albumin loss, respectively,in patients with kidney disease, and determine the most appropriatetime of collection.

Methods: Eighty-three patients were recruited from a renal outpatientclinic. In a 24 h period, each collected an early-morning urine(EMU), second and third voids, and the remaining urine passedthat day. PCR and ACR were determined in random urines and comparedwith 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 rs > 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 h (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 (AUCbetween 0.99 and 1.00). EMU and random urines performed equallywell in predicting proteinuria and albuminuria from PCR andACR, respectively.

Conclusions: By careful choice of cut-offs, both PCR and ACR can be usedin patients with kidney disease to rule in or rule out abnormal24 h losses of protein and albumin. EMU and, importantly, randomsamples can be used as surrogates for 24 h urine collections.

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