The urine albumin-to-creatinine ratio is a reliable indicator for evaluating complications of chronic kidney disease and progression in IgA nephropathy in China.
OBJECTIVE
This study investigated the correlation between the albumin-to-creatinine ratio in the urine and 24-hour urine proteinuria and whether the ratio can predict chronic kidney disease progression even more reliably than 24-hour proteinuria can, particularly in primary IgA nephropathy.


METHODS
A total of 182 patients with primary IgA nephropathy were evaluated. Their mean urine albumin-to-creatinine ratio and 24-hour proteinuria were determined during hospitalization. Blood samples were also analyzed. Follow-up data were recorded for 44 patients. A cross-sectional study was then conducted to test the correlation between these parameters and their associations with chronic kidney disease complications. Subsequently, a canonical correlation analysis was employed to assess the correlation between baseline proteinuria and parameters of the Oxford classification. Finally, a prospective observational study was performed to evaluate the association between proteinuria and clinical outcomes. Our study is registered in the Chinese Clinical Trial Registry, and the registration number is ChiCTR-OCH-14005137.


RESULTS
A strong correlation (r=0.81, p<0.001) was found between the ratio and 24-hour proteinuria except in chronic kidney disease stage 5. First-morning urine albumin-to-creatinine ratios of ≥125.15, 154.44 and 760.31 mg/g reliably predicted equivalent 24-hour proteinuria 'thresholds' of ≥0.15, 0.3 and 1.0 g/24 h, respectively. In continuous analyses, the albumin-to-creatinine ratio was significantly associated with anemia, acidosis, hypoalbuminemia, hyperphosphatemia, hyperkalemia, hypercholesterolemia and higher serum cystatin C. However, higher 24-hour proteinuria was only associated with hypoalbuminemia and hypercholesterolemia. Higher tubular atrophy and interstitial fibrosis scores were also associated with a greater albumin-to-creatinine ratio, as observed in the canonical correlation analysis. Finally, the albumin-to-creatinine ratio and 24-hour proteinuria were associated with renal outcomes in univariate analyses.


CONCLUSIONS
This study supports the recommendation of using the albumin-to-creatinine ratio, rather than 24-hour proteinuria, to monitor proteinuria and prognosis in primary IgA nephropathy.
Guangzhou University of Traditional Chinese Medicine, Guangzhou, Guangdong, PR, China.
Lu
L
Huan
The First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine, Department of Nephrology, Guangzhou, Guangdong, PR, China.
Luo
L
Yuezhong
The First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine, Department of Nephrology, Guangzhou, Guangdong, PR, China.
Wang
W
Chao
The First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine, Department of Nephrology, Guangzhou, Guangdong, PR, China.
Tu
T
HaiTao
D000328:Adult; D000419:Albuminuria / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D002681:China; D003404:Creatinine / Q000652:urine*; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005922:Glomerulonephritis, IGA / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011507:Proteinuria / Q000652:urine; D051436:Renal Insufficiency, Chronic / Q000145:classification / Q000652:urine*; D013997:Time Factors; D055815:Young Adult
D015415:Biomarkers; D003404:Creatinine