Random spot urine protein/creatinine ratio is unreliable for estimating 24-hour proteinuria in individual systemic lupus erythematosus nephritis patients.
BACKGROUND
Recently the American Rheumatologic Association (ARA) recommended random spot urine protein/creatinine ratio (P/C) to monitor systemic lupus erythematosus (SLE) glomerulonephritis (GN). Shortly afterward, 2 works were published, designated Study 1 and Study 2, which are the only studies to test spot P/C in SLE GN. Here we evaluate Study 1 and Study 2, which came to different conclusions.


METHODS
Study 1 compared spot P/C to the P/C of intended 24-hour collections >50% complete, which reliably estimates 24-hour proteinuria. Study 2 compared spot P/C to the protein content of intended 24-hour collections >80% complete. To compare studies, Study 2 data were converted to P/C ratios.


RESULTS
Study 1 and Study 2 were found to be in agreement. Both showed that spot P/C and 24-hour P/C were highly correlated, but only when compared over the entire P/C range (0-8.0) (r = 0.842). Over the P/C range 0.5-3.0 (the most common P/C range encountered in SLE GN), correlation was present, but concordance was poor, rendering random P/C ratio unreliable.


CONCLUSIONS
Random spot P/C ratio is unreliable for detecting moderate proteinuria change. For example, random spot P/C would not reliably diagnose British Isles Lupus Assessment Group (BILAG) Category A or B proteinuric flares.
Hebert
Lee A
LA
Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA. lee.hebert@osumc.edu
Birmingham
Daniel J
DJ
Shidham
Ganesh
G
Rovin
Brad
B
Nagaraja
H N
HN
Yu
Chack-Yung
CY
D000328:Adult; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000175:diagnosis / Q000652:urine*; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000150:complications / Q000175:diagnosis / Q000652:urine*; D015203:Reproducibility of Results; D013997:Time Factors; D016482:Urinalysis / Q000592:standards; D055815:Young Adult
D003404:Creatinine