Determining the Relationship between Urine Creatinine and Urine Osmolality; And a Probable Correction Factor for Hypothetical Ratios for Estimating 24-Hour Urine Protein

Aims and Objectives: The aim of this study was to determine the relationship between urine creatinine and osmolality, and the probable correction factor for spot urine protein/creatinine ratio (SUPCR) and spot urine protein/osmolality ratio (SUPOR) for estimating 24-hour urine protein. Methodology: Creatinine and osmolality were evaluated in both spot and 24-hour urine samples. SUPCR, SUPOR, creatinine clearance (ClCr) and 24-hour urine protein (24HUP) were determined. The association between spot urine creatinine (SUCr) and spot urine osmolality (SUOsm) was determined. Spot urine creatinine (SUCr)/SUOsm ratio (SUCOR) was compared in 4 different groups with different levels of proteinuria (defined as 24HUP≥0.3g) and renal function (renal impairment defined as ClCr Results: The mean SUCr (137.21 ± 98.47mg/dl) was about twice mean 24HUCr (77.87 ± 39.62mg/dl), p 2 O) was about twice mean 24HUOsm (284 ± 216mOsm/kgH 2 O), p SUCOR ≡ 24HUCOR ≡ 0.423 (0.371-0.590). SUPOR ≡ SUPCR x Constant (0.423 ± 0.493). Conclusion: Spot urine contained about twice the concentration of creatinine and osmolality as in 24-hour urine. SUCr was a predictor of SUOsm. The ratio of creatinine to osmolality in both spot urine and 24-hour urine samples appeared to be constant. The correction factor for SUPOR was SUPCR x SUCOR (Constant 0.423±0.493). Future researches would be required to validate this correction factor.