Estimation of quantitative proteinuria by using the protein-creatinine ratio in random urine samples

The protein-creatinine ratio was measured in urine samples obtained at three different times of the day and compared to the 24-hour protein excretion in 51 patients with a wide spectrum of renal function and proteinuria. A linear correlation, which was highly significant, was found between the two variables. The higher correlation was found in urine samples obtained at 08.00 and at 12.00 h and the lowest in samples obtained at 16.00 h. This correlation did not depend on the degree of proteinuria or on the sex of the patients, but was slightly dependent on the glomerular filtration rate. The protein-creatinine ratio was essentially identical with the 24-hour protein excretion. Thus, the normal range of proteinuria was represented by a ratio of less than 0.2, while nephrotic patients had a ratio above 3.5. We suggest that the protein-creatinine ratio in random urine samples could replace the timed collection methods at least for follow-up and screening.