title: Comparison between the three most popular formulae to estimate renal function, in subjects 75 years of age or older.
abstract: OBJECTIVE
  The aim of the study was to compare the accuracy of three formulae that estimate creatinine clearance (CL(CR)), in elderly hospitalized patients: the Cockcroft-Gault (CG) formula and the Modification of Diet in Renal Disease formulae with 4 and 6 variables (MDRD4 and MDRD6).
  
  
  METHODS
  A prospective, cross-sectional, observational study was conducted in four hospital geriatric wards. Consecutive patients admitted to the wards who were aged ≥75 years and had an indwelling urinary catheter for the purpose of care were eligible for enrolment. CL(CR) was determined via four methods: measurement of CL(CR) from plasma and urine creatinine plus 24-h urine volume; the CG formula; and the MDRD4 and MDRD6 formulae. Moderate and severe renal impairments were defined as a CL(CR) of 30.0-59.9 and <30.0 mL/min, respectively.
  
  
  RESULTS
  A total of 157 patients were included. Their mean age (±SD) was 86.5 ± 6.1 (range 75-105) years and 46.5 % were male. The median values and interquartile ranges (IQRs) (in mL/min) were 44.0 (IQR 32.1-64.5) for measured CL(CR), 42.1 (IQR 31.3-56.3) for CG-estimated CL(CR), 64.3 (IQR 49.8-81.7) for MDRD4-estimated CL(CR) and 49.3 (IQR 37.4-63.4) for MDRD6-estimated CL(CR) (respectively, p < 0.05, p < 0.001 and p = 0.44 compared with measured CL(CR)). Biases (±SD) for CG, MDRD4 and MDRD6 CL(CR) estimates were -3.6 (±22.2), 19.3 (±26.4) and 2.4 (±22.5) mL/min, respectively. When estimated CL(CR) values were assessed against the measured value, it was found that misclassification of renal impairment (absent/moderate/severe) occurred in 41 % of patients when using the CG, in 40 % when using the MDRD6, and in 45 % when using the MDRD4. The 30 % accuracies of the three formulae were 63 % for CG, 37 % for MDRD4 and 59 % for MDRD6.
  
  
  CONCLUSIONS
  In elderly hospitalized patients, CG and MDRD6 gave better predictions for measured CL(CR) than MDRD4, with no significant difference between them.
authors.affiliation: Service de Gériatrie, Hôpital Charles Foix et Université UPMC-Paris, Ivry-sur-Seine, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Chauvelier
authors.forename: Renaud
authors.initials: R
authors.lastname: Péquignot
authors.forename: Abdelfarouk
authors.initials: A
authors.lastname: Amzal
authors.forename: Olivier
authors.initials: O
authors.lastname: Hanon
authors.forename: Joel
authors.initials: J
authors.lastname: Belmin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003404:Creatinine / Q000097:blood* / Q000652:urine*; D003430:Cross-Sectional Studies; D005260:Female; D006760:Hospitalization; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D011446:Prospective Studies; D051437:Renal Insufficiency / Q000175:diagnosis*
chemical_list: D003404:Creatinine