Assessment of quantitative proteinuria using random urine protein/creatinine index at different times of the day

To determine the usefulness of measuring protein/creatinene index [PCI] in random urine specimens as an alternative to 24 hour urine protein excretion. Design: Prospective study for 7 months commencing from August 1994. Setting: Measurement of PCI in 3 random urine specimens collected at 8.00, 12.00 and 16.00 hrs were compared with daily urine protein excretion. Participants: A total of 250 individuals including 125 healthy control subjects [100 aged >/= /15 years, 25 aged < 15 years], and 125 patients with proteinuria who were subdivided according to age [100 aged >15 years, 25 aged < 15 years], renal function [69 with normal renal function, 56 with impaired renal function] or protein excretion [61 with proteinuria < 1.0 g/day, 64 with proteinuria >/= /1.0 g/day]. Main outcome measures: Measures were 24 hour urine protein excretion [P24] including that corrected according to surface area [P24/1.73], protein/creatinine index in 24 hour specimen [24PC] and in random specimens of morning [PC8], midday [PC12] and afternoon [PC16]. Student's unpaired t-test, analysis of variance [F test] and linear regression analysis were used for data evaluation. Main Numerical similarity was noted in mean values of 24PC, PC8, 12, 16 with P24 and P24/ 1.73. Correlation studies involving all subjects [n = 250] revealed highly significant correlations [P < 0.001] between random PCI and each of 24 PC [r = 0.978], P24 [r = 0.889] and P24/1.73 [r = 0.912]. The correlations were higher in proteinuric patients, irrespective of age, renal function and degree of proteinuria, than in healthy subjects, and with indices of random specimens obtained at 12.00 and 16.00 that at 8.00 hrs. The PCI of random urine specimen is strongly related to timed protein excretion making its measurement a suitable and convenient alternative to timed collection particularly for follow up and screening purposes