title: Discordance between serum creatinine and creatinine clearance for identification of ED patients with abdominal pain at risk for contrast-induced nephropathy.
abstract: OBJECTIVE
  Despite creatinine clearance (CrCl) being a better estimate of renal function, serum creatinine (Cr) is more commonly used to screen for renal insufficiency in patients scheduled for an enhanced abdominal computed tomography (CT) in an attempt to reduce the likelihood of contrast-induced nephropathy (CIN). Our objective was to determine the incidence of renal insufficiency (a CrCl <60 mL/min) among patients who have serum Cr below 1.5 mg/dL (the most commonly accepted Cr cutoff for the administration of intravenous contrast). This study was conducted in a population of emergency department patients with acute abdominal pain being considered for CT scan.
  
  
  METHODS
  We performed post hoc analysis of a prospective cross-sectional study that enrolled nongravid adults with acute nontraumatic abdominal pain. Patients on dialysis were excluded. The data that we collected included demographics, history, duration/description of pain, patient reported weight, laboratory data, imaging studies, and final diagnosis. Creatinine clearance values (< or >60 mL/min) were compared to Cr values of 1.0, 1.2, 1.5, and 1.8 mg/dL to determine the percentage of patients at risk for nephropathy after contrast injection at each Cr cutoff. Descriptive statistics were used with 95% confidence intervals (CIs).
  
  
  RESULTS
  Seven hundred sixty-five patients were enrolled; 59% (451/765) had an abdominal CT scan. Of 108 patients with CrCl less than 60 mL/min, 59 patients had a Cr less than 1.8 mg/dL (55%; 95% CI, 45%-64%); 43 had a Cr less than 1.5 mg/dL, the most commonly accepted Cr cutoff for contrast administration (40%; 95% CI, 31%-50%); 21 patients had a Cr less than 1.2 mg/dL (19%; 95% CI, 12%-28%); and 10 had a Cr less than 1.0 mg/dL (9%; 95% CI, 5%-16%).
  
  
  CONCLUSIONS
  The most commonly used Cr cutoff (1.5 mg/dL) for contrast administration fails to identify 40% of the patients at risk for CIN. Future studies should address whether using CrCl rather than serum Cr decreases the incidence of contrast-induced nephropathy.
authors.affiliation: Department of Emergency Medicine, University of Pennsylvania School of Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA 19104-4283, USA. roger.band@uphs.upenn.edu
authors.forename: Roger A
authors.initials: RA
authors.lastname: Band
authors.forename: David F
authors.initials: DF
authors.lastname: Gaieski
authors.forename: Angela M
authors.initials: AM
authors.lastname: Mills
authors.forename: Keara L
authors.initials: KL
authors.lastname: Sease
authors.forename: Frances S
authors.initials: FS
authors.lastname: Shofer
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Robey
authors.forename: Judd E
authors.initials: JE
authors.lastname: Hollander
mesh_terms: D015746:Abdominal Pain / Q000097:blood* / Q000145:classification / Q000000981:diagnostic imaging; D058186:Acute Kidney Injury / Q000139:chemically induced*; D000328:Adult; D003287:Contrast Media / Q000009:adverse effects*; D003404:Creatinine / Q000097:blood* / Q000493:pharmacokinetics; D003430:Cross-Sectional Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D003404:Creatinine