title: Clinical Relevance of Differences in Glomerular Filtration Rate Estimations in Frail Older People by Creatinine- vs. Cystatin C-Based Formulae.
abstract: The risk of incorrect medication dosing is high in frail older people. Therefore, accurate assessment of the glomerular filtration rate is important.
  
  
  
  The objective of this study was to compare the estimated glomerular filtration rate using creatinine- and cystatin C-based formulae, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, in frail older people. We hypothesized that frailty determines the difference between the creatinine- and cystatin C-based formulae.
  
  
  
  The mean difference between CKD-EPI creatinine and cystatin C was determined using (cross-sectional) data of 55 patients (mean age 73 years) admitted to a psychiatric ward for older adults. The level of agreement of these estimations was assessed by a Bland-Altman analysis. In all patients, the Rockwood's Frailty Index was derived and correlated with the mean difference between CKD-EPI creatinine and cystatin C.
  
  
  
  The mean difference between CKD-EPI creatinine (mean 71.2 mL/min/1.73 m2) and CKD-EPI cystatin C (mean 57.6 mL/min/1.73 m2) was 13.6 mL/min/1.73 m2(p < 0.0001). The two standard deviation limit in the Bland-Altman plot was large (43.2 mL/min/1.73 m2), which represents a low level of agreement. The Frailty Index did not correlate with the mean difference between the creatinine- and cystatin C-based glomerular filtration rate (Pearson correlation coefficient 0.182, p = 0.184).
  
  
  
  There was a significant gap between a creatinine- and cystatin C-based estimation of glomerular filtration rate, irrespective of frailty. The range of differences between the commonly used estimated glomerular filtration rate formulae might result in clinically relevant differences in drug prescription and differences in chronic kidney disease staging.
authors.affiliation: Department of Geriatrics, Radboudumc, Nijmegen, The Netherlands. jacobs.anne@gmail.com.|Department of Geriatric Psychiatry, Pro Persona Mental Health Care, Nijmegen/Arnhem, The Netherlands. jacobs.anne@gmail.com.|Department of Pharmacology-Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands. jacobs.anne@gmail.com.|Heilige Geeststraat 14, 5664 AV, Geldrop, The Netherlands. jacobs.anne@gmail.com.
authors.forename: Anne
authors.identifier: 0000-0001-8181-5612
authors.initials: A
authors.lastname: Jacobs
authors.affiliation: Department of Geriatrics, Radboudumc, Nijmegen, The Netherlands.|Department of Geriatric Psychiatry, Pro Persona Mental Health Care, Nijmegen/Arnhem, The Netherlands.
authors.forename: Carolien
authors.initials: C
authors.lastname: Benraad
authors.affiliation: Department of Nephrology, Radboudumc, Nijmegen, The Netherlands.
authors.forename: Jack
authors.initials: J
authors.lastname: Wetzels
authors.affiliation: Department of Geriatrics, Radboudumc, Nijmegen, The Netherlands.|Radboudumc Alzheimer Centre, Donders Institute for Brain, Cognition and Behavior, Radboudumc, Nijmegen, The Netherlands.
authors.forename: Marcel Olde
authors.initials: MO
authors.lastname: Rikkert
authors.affiliation: Department of Internal Medicine, Radboudumc, Nijmegen, The Netherlands.|Department of Pharmacology-Toxicology, Radboud University Medical Center, Nijmegen, The Netherlands.|Department of Clinical Pharmacy, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Cornelis
authors.initials: C
authors.lastname: Kramers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D064420:Drug-Related Side Effects and Adverse Reactions / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects*; D006801:Humans; D008297:Male; D008508:Medication Errors; D004364:Pharmaceutical Preparations / Q000008:administration & dosage; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology
chemical_list: D055316:Cystatin C; D004364:Pharmaceutical Preparations; D003404:Creatinine