만성콩팥병 환자에서 알부민뇨와 단백뇨의 상관관계

Abstract

age, 58 ± 18 years) for measurement of albumin, protein and creatinine, and protein electrophoresis (PEP); ABSTRACT

The relationships between albuminuria and proteinuria in CKD patients

Dennis Sung Chul Hong, M.D. Department of Internal Medicine The Graduate School Hanyang University

Background and objectives Recent guidelines recommend to measure albuminuria in approaching chronic kidney disease (CKD). However, whether to adopt urine albumin-to-creatinine ratio (ACR) instead of protein-to-creatinine ratio (PCR) is not clear, and accuracy of estimated albumin excretion rate (eAER) and estimated protein excretion rate (ePER) may be superior to ACR and PCR, respectively. Urine albumin-to-protein ratio (APR) was reported to be useful in detecting tubular proteinuria, but needs to be compared with urine protein electrophoresis (PEP). We addressed these quantitative and qualitative indices for proteinuria in order to find which has more diagnostic utility in patients with CKD.

Design, setting, participants, & measurements Both 24 h-urine and spot urine were collected from 77 stable CKD patients (male, 32; spot urine was obtained immediately after finishing 24 h-urine collection. Based on MDRD and CKD-EPI equation, ePERMDRD, ePERCKD-EPI, eAERMDRD and eAERCKD-EPI were calculated to estimate daily proteinuria and albuminuria. Glomerular CKD was defined by clinical and pathological evidences.

Results Our patients had serum creatinine 1.7 ± 1.1 (mean + SD) mg/dL, 24 h-urine proteinuria 1690 ± 3123 mg/d and albuminuria 1099 ± 1910 mg/d. ACR correlated well with PCR (r2=0.686, P<0.0001), but the presence of albuminuria and proteinuria were not concordant in individuals. The 24-h urine albumin correlated better with eAERMDRD(r2 = 0.951, P <0.001) and eAERCKD-EPI (r2 = 0.953, P <0.001) than ACR (r2 = 0.757, P <0.001), and the 24-h urine protein correlated better with ePERMDRD (r2 = 0.893, P <0.001) and ePERCKD-EPI (r2 = 0.891, P<0.001) than PCR (r2 = 0.885, P <0.001). APR was significantly but not well correlated with the albumin fraction in urine PEP (r2 = 0.33, P <0.001). The albumin fraction obtained from PEP was significantly higher in 59 patients with glomerulopathy than 18 with non-glomerular CKD (49 ± 24% vs. 11 ± 21%, P <0.05) whereas APR had no difference between the groups. In contrast with APR, the albumin fraction in PEP was independently associated with glomerular CKD.

Conclusions Urine albumin should be quantified because microalbuminuria can be revealed in CKD patients without overt proteinuria. To estimate daily proteinuria and albuminuria, ePER and eAER are superior to PCR and ACR, respectively. Compared with APR, urine PEP may be more useful to diagnose glomerular proteinuria.