title: A systematic review of glomerular hyperfiltration assessment and definition in the medical literature.
abstract: OBJECTIVE
  Evaluation of glomerular hyperfiltration (GH) is difficult; the variable reported definitions impede comparisons between studies. A clear and universal definition of GH would help in comparing results of trials aimed at reducing GH. This study assessed how GH is measured and defined in the literature.
  
  
  METHODS
  Three databases (Embase, MEDLINE, CINAHL) were systematically searched using the terms "hyperfiltration" or "glomerular hyperfiltration". All studies reporting a GH threshold or studying the effect of a high GFR in a continuous manner against another outcome of interest were included.
  
  
  RESULTS
  The literature search was performed from November 2012 to February 2013 and updated in August 2014. From 2013 retrieved studies, 405 studies were included. Threshold use to define GH was reported in 55.6% of studies. Of these, 88.4% used a single threshold and 11.6% used numerous thresholds adapted to participant sex or age. In 29.8% of the studies, the choice of a GH threshold was not based on a control group or literature references. After 2004, the use of GH threshold use increased (P<0.001), but the use of a control group to precisely define that GH threshold decreased significantly (P<0.001); the threshold did not differ among pediatric, adult, or mixed-age studies. The GH threshold ranged from 90.7 to 175 ml/min per 1.73 m(2) (median, 135 ml/min per 1.73 m(2)).
  
  
  CONCLUSIONS
  Thirty percent of studies did not justify the choice of threshold values. The decrease of GFR in the elderly was rarely considered in defining GH. From a methodologic point of view, an age- and sex-matched control group should be used to define a GH threshold.
authors.affiliation: Department of Pediatrics, Division of Pediatric Nephrology, University Hospital, Lausanne, Switzerland; francois.cachat@chuv.ch.
authors.forename: Francois
authors.initials: F
authors.lastname: Cachat
authors.affiliation: CRC and Division of Clinical Epidemiology, Department of Health and Community Medicine, University of Geneva University Hospitals of Geneva, Geneva, Switzerland;
authors.forename: Christophe
authors.initials: C
authors.lastname: Combescure
authors.affiliation: Department of Pediatrics, Pediatric Endocrinology Unit, Samaritain Regional Hospital, Vevey, Switzerland; and.
authors.forename: Michel
authors.initials: M
authors.lastname: Cauderay
authors.affiliation: Department of Pediatrics, Division of Pediatric Nephrology, University Hospital, Geneva, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Girardin
authors.affiliation: Department of Pediatrics, Division of Pediatric Nephrology, University Hospital, Lausanne, Switzerland;
authors.forename: Hassib
authors.initials: H
authors.lastname: Chehade
mesh_terms: D005919:Glomerular Filtration Rate; D006801:Humans; D007678:Kidney Glomerulus / Q000503:physiopathology*; D012016:Reference Values; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology*; D009626:Terminology as Topic
keywords: creatinine clearance; diabetic nephropathy; glomerular hyperfiltration; hemodynamics and vascular regulation; hyperfiltration