Background/Purpose: To determine the
utility of an untimed Sample of Urine Protein/Creatinine ratio (S-UPCR) as a
screening test for proteinuria and its ability to accurately measure the level
of proteinuria in Systemic Lupus Erythematosus (SLE).

Methods:
Analysis
was performed on the data available from a single SLE cohort between May
2008-December 2014. Proteinuria was measured in a 24 hour urine sample
collection (24H-P) and with the S-UPCR. Based on the 24H-P, samples were
divided into: Group I: < 0.5, group II: 0.5-0.99, group III: 1-1.99, and
group IV: ≥2g/day. Correlation between 24H-P and S-UPCR was measured.
Agreement was determined by Intraclass Correlation Coefficient (ICC),
Concordance Correlation Coefficient (CCC) and Bland-Altman plot between 24H P/C
and S-UPCR. The best cut-offs for S-UPCR predicting a 24H-P of 0.5, 1.0 and 2.0
g/day were determined with the receiver operating characteristics curve.

Results:
The correlation of 24H-P and S-UPCR for all the samples overall was
high, but the correlation for groups I, II, III and IV was low-moderate. The
agreement for all urine samples overall was appropriate but poor for groups I,
II, III and IV. On the Bland-Altman plot, the dots corresponding for groups III
and IV are outside 2 Standard Deviations signifying poor agreement (Figure 1). S-UPCR
cut-offs for 24H-P of 0.5, 1.0 and 2.0 g/day were 0.08, 0.16 and 0.35 g/mmol

Conclusion:
S-UPCR
can be used as a screening test for proteinuria, and the best cut off value to
predict a 24H-P of 0.5 g/day is 0.08 g/mmol (800 mg/g). S-UPCR is not a valid
test to quantify proteinuria. The accurate level of proteinuria should be
measured by the gold standard test, 24H-P.

Figure
1. Bland-Altman
plot for 24H-P/creatinine content and S-UPCR