title: Chronic kidney disease prevalence and secular trends in a UK population: the impact of MDRD and CKD-EPI formulae.
abstract: BACKGROUND
  Most UK laboratories use the MDRD4 formula to estimate glomerular filtration rate (eGFR), but this may exaggerate chronic kidney disease (CKD) prevalence. In a large adult population, we examined the impact of the more accurate CKD-EPI formulae on prevalence estimates, and on secular trends in prevalence.
  
  
  METHODS
  We extracted all serum creatinine (SCr) results for adults, processed in our laboratory during two 1-year periods (2004, 2009-10). To minimize the effect of acute illness, a patient's lowest SCr was used for each period. eGFR (traceable to isotope dilution mass spectrometry value) was calculated using the MDRD4 and CKD-EPI formulae. Prevalence estimates were compared, with sub-group analysis by age and sex.
  
  
  RESULTS
  In 2004, 102 322 patients had SCr tested (35.4% of the adult population), rising to 123 121 (42.3%) in 2009-10. The proportion tested rose with age to 86% of 85- to 89-year olds. The prevalence of CKD stages 3-5 was lower with the CKD-EPI formulae than the MDRD4 formula. The CKD-EPI formulae reclassified 17 014 patients (5.8%) to milder stages of CKD, most commonly from eGFR 60-89 ml/min/1.73m(2) and CKD stage 3A, in women, and in those <70 years old. 5172 patients (1.8%), mostly elderly women, were reclassified to more severe stages of CKD. Between the two time periods, the prevalence of CKD stages 3-5 rose from 5.44% to 5.63% of the population using MDRD4, but was static at 4.94% with CKD-EPI.
  
  
  CONCLUSIONS
  The CKD-EPI formulae, which are more accurate than the MDRD4 formula at higher GFR, reduced the estimated prevalence of CKD stages 3-5 by 0.5% in 2004 and 0.7% in 2009-10. The greatest reclassification was seen in CKD 3A, particularly amongst middle-aged females. The minor rise in CKD prevalence between 2004 and 2009-10 seen with the MDRD4 formula was not confirmed with the CKD-EPI formulae. The CKD-EPI formulae may reduce overdiagnosis of CKD, but further assessment in the elderly is required before widespread implementation.
authors.affiliation: John Stevenson Lynch Renal Unit, Crosshouse Hospital, Kilmarnock, KA2 0BE, UK.
authors.forename: F J
authors.initials: FJ
authors.lastname: Gifford
authors.forename: S
authors.initials: S
authors.lastname: Methven
authors.forename: D E
authors.initials: DE
authors.lastname: Boag
authors.forename: E M
authors.initials: EM
authors.lastname: Spalding
authors.forename: M S
authors.initials: MS
authors.lastname: Macgregor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003404:Creatinine / Q000097:blood; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000453:epidemiology*; D007677:Kidney Function Tests / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012606:Scotland / Q000453:epidemiology; D055815:Young Adult
chemical_list: D003404:Creatinine