title: Probability of reduced renal function after contrast-enhanced CT: a model based on serum creatinine level, patient age, and estimated glomerular filtration rate.
abstract: OBJECTIVE
  The objectives of our study were to develop a model to predict the probability of reduced renal function after outpatient contrast-enhanced CT (CECT)--based on patient age, sex, and race and on serum creatinine level before CT or directly based on estimated glomerular filtration rate (GFR) before CT--and to determine the relationship between patients with changes in creatinine level that characterize contrast-induced nephropathy and patients with reduced GFR after CECT.
  
  
  METHODS
  Of 5,187 outpatients who underwent CECT, 963 (18.6%) had serum creatinine levels obtained within 6 months before and 4 days after CECT. The estimated GFR was calculated before and after CT using the four-variable Modification of Diet in Renal Disease (MDRD) Study equation. Pre-CT serum creatinine level, age, race, sex, and pre-CT estimated GFR were tested using multiple-variable logistic regression models to determine the probability of having an estimated GFR of < 60 and < 45 mL/min/1.73 m(2) after CECT. Two thirds of the patients were used to create and one third to test the models. We also determined discordance between patients who met standard definitions of contrast-induced nephropathy and those with a reduced estimated GFR after CECT.
  
  
  RESULTS
  Significant (p < 0.002) predictors for a post-CT estimated GFR of < 60 mL/min/1.73 m(2) were age, race, sex, pre-CT serum creatinine level, and pre-CT estimated GFR. Sex, serum creatinine level, and pre-CT estimated GFR were significant factors (p < 0.001) for predicting a post-CT estimated GFR of < 45 mL/min/1.73 m(2). The probability is [exp(y) / (1 + exp(y))], where y = 6.21 - (0.10 x pre-CT estimated GFR) for an estimated GFR of < 60 mL/min/1.73 m(2), and y = 3.66 - (0.087 x pre-CT estimated GFR) for an estimated GFR of < 45 mL/min/1.73 m(2). A discrepancy between those who met contrast-induced nephropathy criteria by creatinine changes and those with a post-CT estimated GFR of < 60 mL/min/1.73 m(2) was detected in 208 of the 963 patients (21.6%).
  
  
  CONCLUSIONS
  The probability of a reduced estimated GFR after CECT can be predicted by the pre-CT estimated GFR using the four-variable MDRD equation. Furthermore, standard criteria for contrast-induced nephropathy are poor predictors of poor renal function after CECT. Criteria need to be established for what is an acceptable risk to manage patients undergoing CECT.
authors.affiliation: Imaging Institute, Cleveland Clinic, 9500 Euclid Ave., Desk Hb6, Cleveland, OH 44195, USA. hertsb@ccf.org
authors.forename: Brian R
authors.initials: BR
authors.lastname: Herts
authors.forename: Erika
authors.initials: E
authors.lastname: Schneider
authors.forename: Nancy
authors.initials: N
authors.lastname: Obuchowski
authors.forename: Emilio
authors.initials: E
authors.lastname: Poggio
authors.forename: Anil
authors.initials: A
authors.lastname: Jain
authors.forename: Mark E
authors.initials: ME
authors.lastname: Baker
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D000367:Age Factors; D002908:Chronic Disease; D003287:Contrast Media / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000097:blood* / Q000139:chemically induced* / Q000175:diagnosis / Q000503:physiopathology; D007677:Kidney Function Tests / Q000706:statistics & numerical data*; D008954:Models, Biological; D015233:Models, Statistical; D011336:Probability; D012372:ROC Curve; D012737:Sex Factors; D014057:Tomography, X-Ray Computed / Q000009:adverse effects
chemical_list: D003287:Contrast Media; D003404:Creatinine