Résumé
BACKGROUND: The urinary protein to creatinine ratio in a single voided random urine sample has been widely used as an estimation of 24 hour urine protein excretion because of inconvenience and frequent collection errors during timed collection of 24 hour urine. But the protein to creatinine ratio also showed frequent estimating error, overestimation or underestimation. We thought that protein to creatinine ratio adjusted by daily creatinine excretion estimated by Cockroft-Gault equation can be more accurate than protein to creatinine ratio and compared them as follows. METHODS: This study consisted of 81 patients whose 24 hour urine protein excretion and random spot urine protein to creatinine ratio were measured concomitantly. There was no significant change of body weight or serum creatinine change around the study day. The modified protein to creatinine ratio could be estimated from the measured protein to creatinine ratio in a random spot urine sample by multiplying the ratio by the expected daily creatinine excretion estimated by Cockroft-Gault equation. These results were compared with well collected 24 hour urine protein. RESULTS: The difference between protein to creatinine ratio and 24 hour urine protein was 0.87+/-1.13, on the other hand, the difference between modified protein to creatinine ratio and 24 hour urine protein was 0.52+/-0.65 (p<0.05). Correlation coefficients between protein to creatinine ratio, modified protein to creatinine ratio and 24 hour urine protein were 0.877, 0.957 respectively. CONCLUSION: The protein to creatinine ratio modified by the expected daily creatinine excreation rate calculated by Cockfort-Gault equation was more accurate than simple protein to creatinine ratio.