title: Glomerular filtration rate in prospective living kidney donors.
abstract: OBJECTIVE
  Measurements of glomerular filtration rate (GFR) are frequently interpreted assuming a linear variation with age. Nonlinear relationships may give a better representation of the changes associated with normal ageing.
  
  
  METHODS
  This was a retrospective study of 904 subjects (468 women, 436 men; age range 18-84 years) undergoing assessment as prospective living kidney donors. GFR was evaluated from (51)Cr-EDTA plasma clearance using blood samples taken at 2, 3 and 4 h. The slope-intercept GFR was corrected for body surface area (BSA) using the Haycock formula and for the fast exponential using the Brochner-Mortensen equation. The relationship between age, gender and GFR was examined using best-fit curve analysis. Nonlinear relationships with age were explored using fractional polynomials.
  
  
  RESULTS
  There was no gender difference in BSA-corrected GFR over five decades of age (P = 0.40). However, female donors with a body mass index >30 kg/m(2) had a statistically significantly lower GFR than nonobese women (P < 0.01). The best-fit relationship between age and GFR was nonlinear and described using a fractional polynomial model of degree 1 (GFR = 103.9-0.0061 × Age(2) mL/min/1.73 m(2)) with a root mean standard error of 12.9 mL/min/1.73 m(2). The residual variance for this model was significantly smaller than for the best-fit linear model (P = 0.006).
  
  
  CONCLUSIONS
  GFR measurements in prospective living kidney donors are best corrected for age using a nonlinear relationship.
authors: Department of Nuclear Medicine, Guy's and St. Thomas NHS Foundation Trust, King's College Academic Health Partners, London, UK, glen.blake@kcl.ac.uk.
authors: Glen M
authors: GM
authors: Blake
authors: Christopher
authors: C
authors: Sibley-Allen
authors: Rachel
authors: R
authors: Hilton
authors: Lisa
authors: L
authors: Burnapp
authors: Masood R
authors: MR
authors: Moghul
authors: David
authors: D
authors: Goldsmith
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001830:Body Surface Area; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000502:physiology*; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012189:Retrospective Studies; D012737:Sex Factors; D009927:Tissue and Organ Procurement; D055815:Young Adult