title: Measures of Urinary Protein and Albumin in the Prediction of Progression of IgA Nephropathy.
abstract: Proteinuria is an independent predictor for IgA nephropathy (IgAN) progression. Urine albumin-to-creatinine ratio (ACR), protein-to-creatinine ratio, and 24-hour urine protein excretion (UPE) are widely used for proteinuria evaluation in clinical practice. Here, we evaluated the association of these measurements with clinical and histologic findings of IgAN and explored which was the best predictor of IgAN prognosis.
  
  
  
  Patients with IgAN were followed up for ≥12 months, were diagnosed between 2003 and 2012, and had urine samples available (438 patients). Spot urine ACR, protein-to-creatinine ratio, and 24-hour UPE at the time of renal biopsy were measured on a Hitachi Automatic Biochemical Analyzer 7180 (Hitachi, Yokohama, Japan).
  
  
  
  In our patients, ACR, protein-to-creatinine ratio, and 24-hour UPE were highly correlated (correlation coefficients: 0.71-0.87). They showed good relationships with acknowledged markers reflecting IgAN severity, including eGFR, hypertension, and the biopsy parameter (Oxford severity of tubular atrophy/interstitial fibrosis parameter). However, only ACR presented with positive association with the Oxford segmental glomerulosclerosis/adhesion parameter and extracapillary proliferation lesions. The follow-up time was 37.0 (22.0-58.0) months, with the last follow-up on April 18, 2014. In total, 124 patients reached the composite end point (30% eGFR decline, ESRD, or death). In univariate survival analysis, ACR consistently had better performance than protein-to-creatinine ratio and 24-hour UPE as represented by higher area under the curve using time-dependent survival analysis. When adjusted for well known risk factors for IgAN progression, ACR was most significantly associated with the composite end point (hazard ratio, 1.56 per 1-SD change of standard normalized square root-transformed ACR; 95% confidence interval, 1.29 to 1.89; P<0.001). Compared with protein-to-creatinine ratio and 24-hour UPE, addition of ACR to traditional risk factors resulted in more improvement in the predictive ability of IgAN progression (c statistic: ACR=0.70; protein-to-creatinine ratio =0.68; 24-hour UPE =0.69; Akaike information criterion: ACR=1217.85; protein-to-creatinine ratio =1229.28; 24-hour UPE =1234.96; P<0.001).
  
  
  
  In IgAN, ACR, protein-to-creatinine ratio, and 24-hour UPE had comparable association with severe clinical and histologic findings. Compared with protein-to-creatinine ratio and 24-hour UPE, ACR showed slightly better performance in predicting IgAN progression.
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Yan-Feng
authors.initials: YF
authors.lastname: Zhao
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Liu
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Su-Fang
authors.initials: SF
authors.lastname: Shi
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Ji-Cheng
authors.initials: JC
authors.lastname: Lv
authors.affiliation: Renal Division, Department of Medicine, Peking University First Hospital, Beijing, China.|Institute of Nephrology, Peking University, Beijing, China.|Key Laboratory of Renal Disease, Ministry of Health of China, Beijing, China; and.|Key Laboratory of Chronic Kidney Disease Prevention and Treatment (Peking University), Ministry of Education, Beijing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000652:urine*; D003404:Creatinine / Q000652:urine; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D005922:Glomerulonephritis, IGA / Q000150:complications / Q000503:physiopathology / Q000652:urine*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011507:Proteinuria / Q000652:urine; D015996:Survival Rate; D055815:Young Adult
chemical_list: D003404:Creatinine
keywords: Follow-Up Studies; Glomerulonephritis, IGA; Humans; IgA nephropathy; Kidney Failure, Chronic; Prognosis; Urinalysis; albuminuria; creatinine; proteinuria