Background Proteinuria is the principal urinary biomarker for the screening of Lupus nephritis (LN) and for monitoring disease progression. 24-hour urine collection has been the foundation for monitoring disease activity in patients with LN, but collections are often inaccurate and inconvenient. The European League Against Rheumatism and American College of Rheumatology have recommended the urine protein/creatinine ratio (UPCR) for use in management of LN.
Objectives We aimed to evaluate the diagnostic accuracy of the morning sample of UPCR compared with 24-hour urine collection for the detection of proteinuria and to determine the UPCR for different proteinuria ranges in patients with LN.
Methods Three hundred and thirty seven LN patients were enrolled. The correlation between the UPCR in the morning spot urine samples and urinary protein excretion in the 24-hour collections was examined using the Pearson correlation test. The best cutoffs for UPCR predicting a 24-hour protein excretion were determined with the receiver operating characteristic curve (ROC).
Results It was found a good positive correlation between the UPCR and 24-hour protein excretion, with a correlation coefficient (r) of 0.891 (Fig 1). The best cutoff which gave the maximum area under the curve was 0.44 for 0.5 g, 0.92 for 1.0 g, 2.21 for 2.0 g, 2.70 for 3.0 g, 3.49 for 4.0 g and 4.59 for 5.0g.
Conclusions The UPCR can be used as a screening test as a good predictor for proteinuria of LN patients. Also, UPCR is a valuable tool with which to monitor disease progression.
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Disclosure of Interest None declared
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