title: The age related association is more pronounced for cystatin C estimated GFR than for creatinine estimated GFR in primary care patients.
abstract: OBJECTIVE
  There is an age associated change in GFR but this association may be influenced by the method used. The aims of the present study were to assess the association between age and cystatin C and creatinine based glomerular filtration rate estimates in primary care patients, and to determine the proportion of patients with clinically important renal impairment.
  
  
  METHODS
  1552 samples with simultaneous requests for creatinine and cystatin C from 1552 primary care patients in the county of Uppsala, Sweden were analysed. MDRD, CKD-EPI and cystatin C equations were used to calculate glomerular filtration rate (GFR) and the associations between GFR and age were explored.
  
  
  RESULTS
  The yearly change in cystatin C estimated GFR was 1.24 mL/min/1.73 m(2) while the corresponding decline for creatinine estimated GFR was 0.76 mL/min/1.73 m(2) for MDRD and 0.99 mL/min/1.73 m(2) for CKD-EPI.
  
  
  CONCLUSIONS
  The age related association with GFR estimates is smaller for creatinine estimates than for cystatin C estimates. This leads to differences in the number of patients with reduced eGFR detected with the three estimates and the patient treatment will depend on the estimate used. This is not coherent with a good patient care and we thus need to develop new eGFR equations with better agreement between the estimates.
authors.affiliation: Department of Medical Sciences, Section of Clinical Chemistry, Uppsala University, Sweden. Electronic address: johanna.helmersson_karlqvist@medsci.uu.se.
authors.forename: Johanna
authors.initials: J
authors.lastname: Helmersson-Karlqvist
authors.forename: Mats
authors.initials: M
authors.lastname: Flodin
authors.forename: Lars-Olof
authors.initials: LO
authors.lastname: Hansson
authors.forename: Anders
authors.initials: A
authors.lastname: Larsson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D003404:Creatinine / Q000378:metabolism*; D055316:Cystatin C / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology; D055815:Young Adult
chemical_list: D055316:Cystatin C; D003404:Creatinine
keywords: Age; Creatinine; Cystatin C; Glomerular filtration rate