title: Estimating GFR in adult patients with hematopoietic cell transplant: comparison of estimating equations with an iohexol reference standard.
abstract: OBJECTIVE
  Formal evaluation of kidney function before and after hematopoietic cell transplant is important to determine conditioning regimens, type of transplant, and medication dosing. Serum creatinine and estimating equations may not accurately assess kidney function.
  Existing estimating equations for GFR were compared with an iohexol measure of GFR in a prospective cohort study of 50 patients undergoing hematopoietic cell transplant and subsequent care at the Fred Hutchinson Cancer Research Institute from 2009 to 2013. Patients underwent iohexol GFR, serum creatinine, and cystatin C determination at baseline and day 100 posthematopoietic cell transplant. Iohexol GFR measurements were compared with the CKD Epidemiology Collaboration, Inker CKD Epidemiology Collaboration cystatin C with and without serum creatinine, Modification of Diet in Renal Disease, and Cockcroft-Gault estimating equations using Bland-Altman analysis and McNemar's test. The iohexol measurements were also compared with blood samples collected simultaneously on filter paper.
  
  
  RESULTS
  Mean differences between iohexol GFR and eGFR on the basis of Bland-Altman analyses ranged from -20.6 to +15.4 ml/min per 1.73 m(2) at baseline and -12.7 to +12.9 ml/min per 1.73 m(2) at day 100. The CKD Epidemiology Collaboration and Modification of Diet in Renal Disease estimating equations classified 64% of patients with a GFR<90 at baseline compared with 38% by iohexol GFR (P=0.003 and P<0.01, respectively). No statistically significant differences were seen at day 100. The filter paper GFR had a mean difference of 0 at baseline and 5.9 at day 100. Additionally, 21%-37% and 57%-89% of eGFRs were within 10% and 30%, respectively, of the iohexol GFR at baseline, and 16%-34% and 72%-84% were within 10% and 30%, respectively, of the iohexol GFR at day 100; 98% of the filter paper estimates at baseline were within 30%, and 46% were within 10% of iohexol GFR.
  
  
  CONCLUSIONS
  The estimating equations are neither accurate nor precise in the hematopoietic cell transplant population, and clinical decision may require measurement of GFR.
authors.affiliation: Seattle Children's Hospital, University of Washington Seattle, Washington; Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington; and sangeeta.hingorani@seattlechildrens.org.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Hingorani
authors.affiliation: Seattle Children's Hospital, University of Washington Seattle, Washington;
authors.forename: Emily
authors.initials: E
authors.lastname: Pao
authors.affiliation: Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington; and.
authors.forename: Gary
authors.initials: G
authors.lastname: Schoch
authors.affiliation: Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington; and.
authors.forename: Ted
authors.initials: T
authors.lastname: Gooley
authors.affiliation: Division of Pediatric Nephrology, University of Rochester, Rochester, New York.
authors.forename: George J
authors.initials: GJ
authors.lastname: Schwartz
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003287:Contrast Media / Q000008:administration & dosage*; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D018380:Hematopoietic Stem Cell Transplantation / Q000009:adverse effects; D006801:Humans; D007472:Iohexol / Q000008:administration & dosage*; D007668:Kidney / Q000503:physiopathology*; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016896:Treatment Outcome; D014861:Washington; D055815:Young Adult
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D003287:Contrast Media; D055316:Cystatin C; D007472:Iohexol; D003404:Creatinine
keywords: GFR; creatinine; hematopoietic cell transplantation; renal function