title: Predicting kidney transplantation outcomes using proteinuria ascertained from spot urine samples versus timed urine collections.
abstract: BACKGROUND
  Proteinuria has been associated with transplant loss and mortality in kidney transplant recipients. Both spot samples (albumin-creatinine ratio [ACR] and protein-creatinine ratio [PCR]) and 24-hour collections (albumin excretion rate [AER] and protein excretion rate [PER]) have been used to quantify protein excretion, but which measurement is a better predictor of outcomes in kidney transplantation remains uncertain.
  
  
  METHODS
  Observational cohort study.
  
  
  METHODS
  Tertiary care center, 207 kidney transplant recipients who were enrolled in a prospective study to measure glomerular filtration rate. Consecutive patients who met inclusion criteria were approached.
  
  
  METHODS
  ACR and PCR in spot urine samples, AER and PER in 24-hour urine collections.
  
  
  RESULTS
  Primary outcome included transplant loss, doubling of serum creatinine level, or death.
  
  
  METHODS
  Urine and serum creatinine were measured using a modified Jaffé reaction that had not been standardized by isotope-dilution mass spectrometry. Urine albumin was measured by immunoturbidimetry. Urine protein was measured by pyrogallol red molybdate complex formation using a timed end point method.
  
  
  RESULTS
  Mean follow-up was 6.4 years and 22% developed the primary end point. Multivariable-adjusted areas under the receiver operating characteristic curves were similar for the different protein measurements: ACR (0.85; 95% CI, 0.79-0.89), PCR (0.84; 95% CI, 0.79-0.89), PER (0.86; 95% CI, 0.80-0.90), and AER (0.83; 95% CI, 0.78-0.88). C Index values also were similar for the different proteinuria measurements: 0.87 (95% CI, 0.79-0.95), 0.86 (95% CI, 0.79-0.94), 0.88 (95% CI, 0.82-0.94), and 0.86 (95% CI, 0.77-0.95) for log(ACR), log(PCR), log(PER), and log(AER), respectively.
  
  
  CONCLUSIONS
  Single-center study. Measurement of proteinuria was at variable times posttransplantation.
  
  
  CONCLUSIONS
  Spot and 24-hour measurements of albumin and protein excretion are similar predictors of doubling of serum creatinine level, transplant loss, and death. Thus, spot urine samples are a suitable alternative to 24-hour urine collection for measuring protein excretion in this population.
authors.affiliation: Division of Nephrology, Department of Medicine, University of Ottawa, Ottawa.
authors.forename: Hari
authors.initials: H
authors.lastname: Talreja
authors.affiliation: Division of Nephrology, Department of Medicine, University of Ottawa, Ottawa; Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa; Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa.
authors.forename: Ayub
authors.initials: A
authors.lastname: Akbari
authors.affiliation: Division of Nephrology, Department of Medicine, Queen's University, Kingston, Canada.
authors.forename: Christine A
authors.initials: CA
authors.lastname: White
authors.affiliation: Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa.
authors.forename: Tim O
authors.initials: TO
authors.lastname: Ramsay
authors.affiliation: Division of Nephrology, Department of Medicine, University of Ottawa, Ottawa; Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa; Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa.
authors.forename: Swapnil
authors.initials: S
authors.lastname: Hiremath
authors.affiliation: Division of Nephrology, Department of Medicine, University of Ottawa, Ottawa; Kidney Research Centre, Ottawa Hospital Research Institute, Ottawa; Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa. Electronic address: gknoll@ottawahospital.on.ca.
authors.forename: Greg
authors.initials: G
authors.lastname: Knoll
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016030:Kidney Transplantation / Q000401:mortality; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011507:Proteinuria / Q000175:diagnosis* / Q000401:mortality / Q000652:urine*; D013997:Time Factors; D016896:Treatment Outcome; D016482:Urinalysis / Q000379:methods* / Q000592:standards
keywords: 24-hour urine collection; Proteinuria; albumin excretion rate (AER); albumin-creatinine ratio (ACR); albuminuria; end-stage renal disease (ESRD); kidney graft survival; outcomes; protein excretion rate (PER); protein-creatinine ratio (PCR); spot urine sample