Correlation between the protein/creatinine ratio in spot urine and 24-hour urine protein.
BACKGROUND
Measurement of the protein content in a 24-hour urine sample is the definitive method of establishing the presence of abnormal proteinuria. However, the urine collection is cumbersome. The spot urine protein to creatinine ratio seems to be a reliable diagnostic tool for urine protein measurement.


OBJECTIVE
Our aim was to evaluate the spot urine protein/creatinine ratio against 24-h urine total protein excretion in different proteinuria ranges by comparing samples collected simultaneously in patients of Hospital del Mar during the last year.


METHODS
Observational, cross-sectional study of 159 consecutive paired determinations of 24-h urine total protein excretion and the spot urine protein/creatinine ratio (P/C) in renal patients. The strength of the correlation was determined by calculating the intraclass correlation coefficient (ICC) and the Spearman correlation coefficient (SCC).


RESULTS
Among all groups, there was a significant correlation between 24-hour proteinuria and the P/C ratio (SCC: r=0.91, P<0.001). The correlation in different levels of proteinuria were: <300 mg (SCC: r=0.498, P<0.001; ICC: 0.46), 300-3,499 mg (SCC: r=0.828, P<0.001; ICC: 0.66) and ≥3,500 mg (SCC: r=0.181, P=NS; ICC: 0.18).


CONCLUSIONS
In summary, a strong correlation was observed between spot urine protein/creatinine ratio and 24-h urine total protein excretion in proteinuria levels from 300 mg/day to 3,499 mg/day. A lower correlation was also maintained in 24-h urine total protein <300 mg. In our experience, there is no relevant correlation between spot urine protein/creatinine ratio and 24-h urine total protein excretion in nephrotic-range proteinuria.
Servicio de Nefrología, Hospital del Mar, Fundació IMIM, Barcelona, Spain.
Nuria
N
Montero
M José
MJ
Soler
M José
MJ
Pascual
Clara
C
Barrios
Eva
E
Márquez
Eva
E
Rodríguez
Ali
A
Berrada
Marta
M
Riera
Lluís
L
Coca
M Antonia
MA
Orfila
Julio
J
Pascual
D000328:Adult; D000368:Aged; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009404:Nephrotic Syndrome / Q000652:urine; D017410:Practice Guidelines as Topic; D011446:Prospective Studies; D011507:Proteinuria / Q000652:urine*; D051437:Renal Insufficiency / Q000652:urine*; D015203:Reproducibility of Results; D013997:Time Factors; D016482:Urinalysis / Q000379:methods
D003404:Creatinine