title: Estimating baseline kidney function in hospitalized patients with impaired kidney function.
abstract: OBJECTIVE
  Inaccurate determination of baseline kidney function can misclassify acute kidney injury (AKI) and affect the study of AKI-related outcomes. No consensus exists on how to optimally determine baseline kidney function when multiple preadmission creatinine measurements are available.
  
  
  METHODS
  The accuracy of commonly used methods for estimating baseline serum creatinine was compared with that of a reference standard adjudicated by a panel of board-certified nephrologists in 379 patients with AKI or CKD admitted to a tertiary referral center.
  
  
  RESULTS
  Agreement between estimating methods and the reference standard was highest when using creatinine values measured 7-365 days before admission. During this interval, the intraclass correlation coefficient (ICC) for the mean outpatient serum creatinine level (0.91 [95% confidence interval (CI), 0.88-0.92]) was higher than the most recent outpatient (ICC, 0.84 [95% CI, 0.80-0.88]; P<0.001) and the nadir outpatient (ICC, 0.83 [95% CI, 0.76-0.87; P<0.001) serum creatinine. Using the final creatinine value from a prior inpatient admission increased the ICC of the most recent outpatient creatinine method (0.88 [95% CI, 0.85-0.91]). Performance of all methods declined or was unchanged when the time interval was broadened to 2 years or included serum creatinine measured within a week of admission.
  
  
  CONCLUSIONS
  The mean outpatient serum creatinine measured within a year of hospitalization most closely approximates nephrologist-adjudicated serum creatinine values.
authors.affiliation: Department of Medicine, Division of Nephrology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA. edward.siew@vanderbilt.edu
authors.forename: Edward D
authors.initials: ED
authors.lastname: Siew
authors.forename: T Alp
authors.initials: TA
authors.lastname: Ikizler
authors.forename: Michael E
authors.initials: ME
authors.lastname: Matheny
authors.forename: Yaping
authors.initials: Y
authors.lastname: Shi
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Schildcrout
authors.forename: Ioana
authors.initials: I
authors.lastname: Danciu
authors.forename: Jamie P
authors.initials: JP
authors.lastname: Dwyer
authors.forename: Manakan
authors.initials: M
authors.lastname: Srichai
authors.forename: Adriana M
authors.initials: AM
authors.lastname: Hung
authors.forename: James P
authors.initials: JP
authors.lastname: Smith
authors.forename: Josh F
authors.initials: JF
authors.lastname: Peterson
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000503:physiopathology; D000368:Aged; D000465:Algorithms; D016001:Confidence Intervals; D003404:Creatinine / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology; D012189:Retrospective Studies; D016037:Single-Blind Method; D013997:Time Factors
chemical_list: D003404:Creatinine