A comparative study of spot urine versus 24 hour urine in assessment of proteinuria in varying degree of renal dysfunction
Keywords:Protein -creatinine ratio, Proteinuria, Urine analysis, 24 hours urinary protein
Background: Proteinuria is a condition in which urine contains an excess amount of proteins. The gold standard test for evaluation of proteinuria is 24 hour urinary protein estimation which is a cumbersome process. The rate of urinary protein excretion remains variable and no standard values have been established for timed samples. However since it remains a very simple procedure to perform, evaluation of the predictive nature of the test in comparison to the 24 hour method is necessary. The aim of the study was to compare the 24 hour urinary protein excretion expected from 7 am and 7 pm spot urine protein creatinine ratio with the estimated urine protein from a 24 hours urinary sample collection.
Methods: 55 patients with persistent dipstick positive proteinuria with varying degrees of renal dysfunction were included in this study. Two urine samples were collected, one in the early morning (around 7 am) and other in the evening (around 7 pm). Both samples were used to estimate protein – creatinine ratio and calculate expected 24 hours urinary protein excretion. 24 hours urine protein estimation was done simultaneously and compared.
Results: There was significant positive correlation with both the samples though the better correlation was seen in early morning urine sample than evening sample (r = 0.931 for 7am sample & r = 0.872 in 7 pm sample; p <0.01). The maximum correlation was seen in patients with normal/mild renal dysfunction and non nephrotic range proteinuria while it was lesser in patients with moderate/severe renal dysfunction and nephrotic range proteinuria.
Conclusions: Spot Urine Protein Creatinine Ratio may be used as an alternative for the 24 hour urinary protein excretion as it has a good correlation with the longer method. The early morning sample may be a preferable one.
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