title: Characteristics of population with normal serum creatinine impaired renal function and: the validation of a MDRD formula in a healthy general population.
abstract: OBJECTIVE
  Glomerular filtration rate (GFR) provides the most accurate estimation of renal function. This study investigated the clinical characteristics of patients with impaired renal function having a normal serum creatinine level. We also validated whether the new Modification of Diet in Renal Disease (MDRD) formula can be applied in a healthy general population.
  
  
  METHODS
  A total 393 participants who had serum creatinine concentration below 132.6 micromol/L without underlying diseases were randomly selected on an address basis in Ansan City. According to the level of GFR, they were divided into 3 groups and we analyzed their clinical characteristics. In 75 subjects, who were randomly selected 25 cases in each group based on GFR estimated by Cockcroft-Gault (C-G) formula, true GFR was measured using the 99mTc-DTPA renal clearance method.
  
  
  RESULTS
  A total 393 (male: 106, female: 287) participants were as follows: GFR < 60 ml/min/1.73 m2; 4% (n = 25); 60 < or = GFR < 90 ml/min/1.73 m2; 26.2% (n = 103); GFR > or = 90 ml/min/1.73 m2; 67.4% (n = 265). In the group of decreased GFR, the mean age was older (67.4+/-10.7 vs. 48.7+/-12.8 vs. 39.4+/-8.2 years, p < 0.001), the gender was male (90.33+/-28.77 vs. 110.55+/-31.64, p < 0.001), and amount of proteinuria more increased (0.61 (0.56) vs. 0.33 (0.34) vs. 0.38 (0.33) gm/day, p = 0.007). The accuracy and precision of each formula were assessed by the difference in GFR measured by the 99mTc-DTPA renal clearance method--estimated GFR by each formula (deltaGFR), and the coefficient of determination (r2) of different predictive equations. The results were as follows: deltaGFR = -14.78+/-46.03, r2 = 0.79 (24-hour urinary creatinine clearance), deltaGFR=-16.79+/-57.32, r2 = 0.66 (100/serum creatinine), deltaGFR = 9.54+/-39.18, r2 = 0.87 (C-G formula), deltaGFR = -12.30+/-54.31, r2 = 0.66 (AASK formula), deltaGFR = 8.70+/-37.62, r2 = 0.79 (MDRD formula). Multiple linear regression analysis and logistic regression analysis showed that age, serum creatinine, total cholesterol and 24-hour urinary protein excretion were independently related to GFR and associated with a significant increase in the risk of decrement of GFR.
  
  
  CONCLUSIONS
  From these results, a more accurate assessment of renal function should be required in a population characterized by older age, male gender and more proteinuria. The MDRD study formula and Cockcroft-Gault formula have greater accuracy and precision with true GFR, and this equation can be applied in subjects with healthy general population.
authors.affiliation: Department of Internal Medicine, College of Medicine, Korea University, Ansan, Korea.
authors.forename: Y S
authors.initials: YS
authors.lastname: Kang
authors.forename: K H
authors.initials: KH
authors.lastname: Han
authors.forename: S Y
authors.initials: SY
authors.lastname: Han
authors.forename: H K
authors.initials: HK
authors.lastname: Kim
authors.forename: D R
authors.initials: DR
authors.lastname: Cha
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002940:Circadian Rhythm / Q000502:physiology; D003404:Creatinine / Q000097:blood* / Q000652:urine; D004032:Diet / Q000592:standards*; D005247:Feeding Behavior; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007674:Kidney Diseases / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012016:Reference Values; D012189:Retrospective Studies; D014505:Urban Population
chemical_list: D003404:Creatinine