title: Accuracy and precision of the CKD-EPI and MDRD predictive equations compared with glomerular filtration rate measured by inulin clearance in a Saudi population.
abstract: BACKGROUND
  Predictive equations for estimating glomerular filtration rate (GFR) in different clinical conditions should be validated by comparing with the measurement of GFR using inulin clearance, a highly accurate measure of GFR.
  
  
  OBJECTIVE
  Our aim was to validate the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) equations by comparing it to the GFR measured using inulin clearance in chronic kidney disease (CKD) patients.
  
  
  METHODS
  Cross-sectional study performed in adult Saudi patients with CKD.
  
  
  METHODS
  King Saud University Affiliated Hospital, Riyadh, Saudi Arabia in 2014.
  
  
  METHODS
  We compared GFR measured by inulin clearance with the estimated GFR calculated using CKD-EPI and MDRD predictive formulas.
  
  
  METHODS
  Correlation, bias, precision and accuracy between the estimated GFR and inulin clearance.
  
  
  RESULTS
  Comparisons were made in 31 participants (23 CKD and 8 transplanted), including 19 males (mean age 42.2 [15] years and weight 68.7 [18] kg). GFR using inulin was 51.54 (33.8) mL/min/1.73 m2 in comparison to inulin clearance, the GFR by the predictive equations was: CKD-EPI creatinine 52.6 (34.4) mL/ min/1.73 m2 (P=.490), CKD-EPI cystatin C 41.39 (30.30) mL/min/1.73 m2 (P=.002), CKD creatinine-cystatin C 45.03 (30.9) mL/min/1.73 m2 (P=.004) and MDRD GFR 48.35 (31.5) mL/min/1.73 m2 (P=.028) (statistical comparisons vs inulin). Bland-Altman plots demonstrated that GFR estimated by the CKD-EPI creatinine was the most accurate compared with inulin clearance, having a mean difference (estimated bias) and limits of agreement of -1.1 (15.6,-17.7). By comparison the mean differences for predictive equations were: CKD-EPI cystatin C 10.2 (43.7,-23.4), CKD creatinine-cystatin C 6.5 (29.3,-16.3) and MDRD 3.2 (18.3,-11.9). except for CKD-EPI creatinine, all of the equations underestimated GFR in comparison with inulin clearance.
  
  
  CONCLUSIONS
  When compared with inulin clearance, the CKD-EPI creatinine equation is the most accurate, precise and least biased equation for estimation of GFR in the Saudi population and in all subgroups by age, stage of CKD and transplantation status.
  
  
  CONCLUSIONS
  Small sample size and the study did not include patients with comorbid diseases such as diabetes, hepatitis C virus infection, and other co-morbidities as well as old age ( > 80 years).
authors.affiliation: Professor Jamal Saleh Al-Wakeel, Nephrology Unit,, Department of Medicine,, King Saud University, PO Box 2925 Riyadh, 11461 Saudi Arabia, T: 0096614671531, F: 0096614672671, jwakeel@ksu.edu.sa.
authors.forename: Jamal Saleh
authors.initials: JS
authors.lastname: Al-Wakeel
mesh_terms: D000328:Adult; D000368:Aged; D015897:Comorbidity; D003404:Creatinine / Q000378:metabolism; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000378:metabolism; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007444:Inulin / Q000378:metabolism*; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000503:physiopathology* / Q000601:surgery; D015203:Reproducibility of Results; D012529:Saudi Arabia; D055815:Young Adult
chemical_list: D055316:Cystatin C; D007444:Inulin; D003404:Creatinine