title: Measuring the glomerular filtration rate in different age groups using iohexol, the protocol from the Belgian iohexol study.
abstract: OBJECTIVE
  Measuring the exact glomerular filtration rate (GFR) is difficult. Iohexol can be used instead of inulin or labeled EDTA or DTPA. In recent years, different studies have validated GFR-estimating equations in adults. Validation of these estimations in adolescents and elderly is lacking. With this study, we aim to develop a simplified (only 1-3 blood collections) iohexol protocol to measure the true GFR for patients of all ages and try to develop GFR-estimating equations for adolescents and the elderly.
  
  
  METHODS
  Participants of different ages will be recruited: 50 adolescent (14-18 years) and 30 adults (20-65 years), 60 elderly (65-80 years) and 60 very elderly (80+ years old) stratified based on their GFR. Biometric data, serum creatinine and cystatin C will be measured. After injecting 5 mL iohexol, 9 blood samples will be taken between 20 and 360 min. First, the GFR will be calculated by using the double exponential decay method and different GFRs based on 1-3 blood samples, which will be compared with the GFR of the abovementioned 9 samples. Second, the GFR will be calculated by using new and existing equations and compared to the true GFR.
  
  
  CONCLUSIONS
  The availability of a reliable GFR measurement is important in situations such as screening patients for kidney donation or when taking potentially nephrotoxic treatments. This study will allow us to develop a simplified protocol for measuring the true GFR in all ages and will allow us to validate existing equations and develop new eGFR equations for adolescents and the elderly.
authors.affiliation: Department of General Practice, KULeuven, Leuven, Belgium; IRSS, UCLouvain, Brussels, Belgium. gijs.vanpottelbergh@med.kuleuven.be
authors.forename: G
authors.initials: G
authors.lastname: Van Pottelbergh
authors.forename: L
authors.initials: L
authors.lastname: Hoste
authors.forename: J
authors.initials: J
authors.lastname: Degryse
authors.forename: H
authors.initials: H
authors.lastname: Pottel
authors.forename: K
authors.initials: K
authors.lastname: Claes
authors.forename: N
authors.initials: N
authors.lastname: Demoulin
authors.forename: M
authors.initials: M
authors.lastname: Jadoul
authors.forename: B
authors.initials: B
authors.lastname: Bammens
authors.forename: P
authors.initials: P
authors.lastname: Wallemacq
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007472:Iohexol; D007674:Kidney Diseases / Q000175:diagnosis; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D003287:Contrast Media; D055316:Cystatin C; D007472:Iohexol; D003404:Creatinine