Renal Function
 

Estimated Glomerular Filtration Rate (eGFR)

 
 
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Overview

  • eGFR is the most common means for estimating glomerular filtration rate (GFR) in clinical practice in the context of assessing chronic kidney disease; equations rely on serum creatinine measurements and are adjusted depending on the patient's demographic information.
  • eGFR calculators can be found in the tools section of the app.
    • Stages of Chronic Kidney Disease

    • StageeGFR (ml/min/1.73 m²)
      I ≥90
      I60 - 89
      III30 - 59
      IV15 - 29
      V<15

MDRD Formula

  • The MDRD formula was created for the modification of diet in renal disease (MDRD) study based on data from patients with advanced renal failure. This formula is commonly used by labs to calculate an eGFR to be reported along with the creatinine.
    • Formula

    • eGFR = 186.3 × Creatinine-1.154 × Age-0.203 ( × 0.742 if female) ( × 1.212 if African origin)
  • There are also five-variable (including BUN) and six-variable (including albumin) MDRD formulae for eGFR.
    • Limitations

    • Not validated for patients with normal renal function
    • Not validated for acute kidney injury and for patients with rapidly changing renal function, as the data is from CKD
    • Not accurate in pregnancy, severe malnutrition and in children

CKD-EPI Formula

  • Uses the same variables as the MDRD formula but with a slightly different equation that tends to be more predictive, especially at higher GFRs.
    • Formula

    • eGFR = 141 × (Creatinine/X)Y × 0.993Age ( × 1.018 if female) ( × 1.159 if african origin)

      Female:
         Cr ≤0.7mg/dL (62µmol/L): X = 0.7; Y = -0.329
         Cr >0.7mg/dL (62µmol/L): X = 0.7; Y = -1.209
      Male:
         Cr ≤0.9mg/dL (80µmol/L): X = 0.9; Y = -0.411
         Cr >0.9mg/dL (80µmol/L): X = 0.9; Y = -1.209
    • Limitations

    • Younger patients are more likely to have a higher eGFR and be classified in lower stages of CKD compared to other formulae
    • Older patients (>80 years) are more likely to have a lower eGFR and be classified in higher stages of CKD compared to other formulae
 
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 Bellomo R, Kellum JA, Ronco C. Acute kidney injury. The Lancet. 2012 Aug 31;380(9843):756-66.
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 Koyner JL. Assessment and diagnosis of renal dysfunction in the ICU. CHEST Journal. 2012 Jun 1;141(6):1584-94. Levey AS, Stevens LA, Schmid CH, Zhang YL, Castro AF, Feldman HI, Kusek JW, Eggers P, Van Lente F, Greene T, Coresh J. A new equation to estimate glomerular filtration rate. Annals of internal medicine. 2009 May 5;150(9):604-12. Nankivell BJ. Creatinine Clearance and the Assessment of Renal Function. Australian Prescriber. 2001; 24: 15-17. Richards RJ, Donica MB, Grayer D. Can the Blood Urea Nitrogen/Creatinine Ratio Distinguish Upper From Lower Gastrointestinal Bleeding?. Journal of clinical gastroenterology. 1990 Oct 1;12(5):500-4. Samra M, Abcar AC. False estimates of elevated creatinine. The Permanente Journal. 2012;16(2):51. Schold JD, Navaneethan SD, Jolly SE, Poggio ED, Arrigain S, Saupe W, Jain A, Sharp JW, Simon JF, Schreiber MJ, Nally JV. Implications of the CKD-EPI GFR estimation equation in clinical practice. Clinical Journal of the American Society of Nephrology. 2011 Mar 1;6(3):497-504. Shlipak MG, Katz R, Kestenbaum B, Fried LF, Newman AB, Siscovick DS, Stevens L, Sarnak MJ. Rate of kidney function decline in older adults: a comparison using creatinine and cystatin C. American journal of nephrology. 2009;30(3):171-8.
Traynor J, Mactier R, Geddes CC, Fox JG. How to measure renal function in clinical practice. BMJ: British Medical Journal. 2006 Oct 7;333(7571):733.
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