title: A practical method to measure GFR in people with type 1 diabetes.
abstract: OBJECTIVE
  Improved early diagnostic methods are needed to identify risk for kidney disease in people with type 1 diabetes. We hypothesized that glomerular filtration rate (GFR) measured by iohexol clearance in dried blood spots (DBS) on filter paper would be comparable to plasma (gold-standard) and superior to estimated GFR (eGFR) and, second, that adjustment for ambient blood glucose would improve accuracy and precision of GFR measurement.
  
  
  METHODS
  GFR was measured by iohexol clearance in plasma, DBS, and as estimated by the CKD-Epidemiology Collaboration equations in 15 adults with type 1 diabetes at two visits, one euglycemic and one hyperglycemic.
  
  
  RESULTS
  GFR measured by DBS was more comparable and less biased than GFR cystatin C, serum creatinine, and both combined. GFR was higher during hyperglycemia. Correction for between visit glycemia statistically significantly reduced bias and mean squared error for GFR measured by DBS as compared to gold-standard during euglycemia.
  
  
  CONCLUSIONS
  Iohexol clearance measured with DBS performed better than eGFR methods. Correction for ambient blood glucose improved precision and accuracy of GFR measurement. This method is more convenient than the gold-standard GFR method and may improve screening and diagnostic capabilities in people with type 1 diabetes, especially when GFR is >60ml/min/1.73m(2).
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO; Department of Medicine, Division of Nephrology, University of Colorado Denver, Aurora, CO. Electronic address: David.Maahs@ucdenver.edu.
authors.forename: D M
authors.initials: DM
authors.lastname: Maahs
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Denver, Aurora, CO.
authors.forename: L
authors.initials: L
authors.lastname: Bushman
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Denver, Aurora, CO.
authors.forename: B
authors.initials: B
authors.lastname: Kerr
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO; Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Denver, Aurora, CO.
authors.forename: S L
authors.initials: SL
authors.lastname: Ellis
authors.affiliation: Department of Pediatrics, School of Medicine, University of Colorado Denver, Aurora, CO.
authors.forename: L
authors.initials: L
authors.lastname: Pyle
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO.
authors.forename: K
authors.initials: K
authors.lastname: McFann
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO.
authors.forename: A
authors.initials: A
authors.lastname: Bouffard
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO.
authors.forename: F K
authors.initials: FK
authors.lastname: Bishop
authors.affiliation: Barbara Davis Center for Childhood Diabetes, University of Colorado Denver, Aurora, CO.
authors.forename: N
authors.initials: N
authors.lastname: Nguyen
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Denver, Aurora, CO.
authors.forename: P L
authors.initials: PL
authors.lastname: Anderson
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D003922:Diabetes Mellitus, Type 1 / Q000150:complications* / Q000503:physiopathology*; D003928:Diabetic Nephropathies / Q000175:diagnosis* / Q000209:etiology; D059788:Dried Blood Spot Testing / Q000379:methods; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007472:Iohexol / Q000493:pharmacokinetics; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007472:Iohexol
keywords: Cystatin C; Diabetic kidney disease; Glomerular filtration rate; Hyperglycemia; Serum creatinine; Type 1 diabetes