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NDT Advance Access originally published online on September 5, 2006
Nephrology Dialysis Transplantation 2007 22(2):665; doi:10.1093/ndt/gfl537
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© The Author [2006]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org

Recalibration of population-based GFR formulae by pharmacokinetic methods

Email: sabine.zitta{at}meduni-graz.at

Sir,

In the interesting article ‘Estimating glomerular filtration in the general population: the second Health Survey of Nord-Trondelag (HUNT II)’ by Hallan et al. [1], attention is drawn to the increasing documentation of ‘large underestimation of glomerular filtration rate (GFR) in older subjects using the Cockcroft–Gault formula’. The authors present a new population-based GFR formula and postulate recalibration of such formulae. Unfortunately, they do not discuss explicitly the experimental and mathematical procedures necessary for correct determination of GFR.

As we have shown elsewhere [2,3], underestimation of GFR stems from constant-infusion experiments, theoretically requiring the achievement of steady states, but practically not fulfilling this requirement because of experimental protocols which are generally too short. Despite this obvious weakness, constant-infusion techniques are celebrated as ‘gold standards’.

It appears to us that the only mathematically correct, and at the same time clinically practicable solution, for the GFR standardization problem consists in the use of pharmacokinetic models that are adapted to dynamic concentration courses of physiologically suitable markers. This appears to be all the more valid, since the theoretically correct technique of GFR determination by constant-infusion experiments using infinitely long experimental protocols can be shown with mathematical rigor to be a special case within the wider concept of kinetic techniques.

Kinetic methods are already successfully applied in many fields of biomedicine and biotechnology [4], and a renewed discussion of the GFR-standardization problem as stimulated by the intriguing biometric study by Hallan et al. [1] could pave the way to recalibrated population-based formulae for future nephrological studies.

Conflict of interest statement. None declared.

S. Zitta1, H. Holzer1, G. Reibnegger2 and W. Estelberger3

1Department of Medicine
Division of Nephrology
Medical University Graz
2Institute of Medical Chemistry
Medical University Graz
3Institute for Analysis and Scientific Computing
Technical University Vienna
Austria

References

  1. Hallan S, Astor B, Lydersen S. (2006) Estimating glomerular filtration in the general population: the second Health Survey of Nord-Trondelag (HUNT II). Nephrol Dial Transplant 21:1525–1533.[Abstract/Free Full Text]
  2. Estelberger W, Petek W, Zitta S, et al. (1995) Determination of glomerular filtration rate by identification of sinistrin kinetics. Eur J Clin Chem Clin Biochem 33:201–209.[Web of Science][Medline]
  3. Zitta S, Stoschitzky K, Zweiker R, et al. (2000) Dynamic renal function testing by compartmental analysis: assessment of renal functional reserve in essential hypertension. Nephrol Dial Transplant 15:1162–1169.[Abstract/Free Full Text]
  4. Carson E, Godfrey K, Reeve J. (1982) A review of modelling and the role of dynamic tracer studies in metabolism. In Cramp D (Ed.). Quantitative approaches to metabolism(Wiley, Chichester) pp. 1–72.[Abstract/Free Full Text]

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This Article
Right arrow Extract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
22/2/665    most recent
gfl537v1
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Google Scholar
Right arrow Articles by Zitta, S.
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