We thank doctors Dharmarayan and Yoo for their comments on our article.
1In line with the literature and our results, they found a substantial lack of consistency among the results of different formulas estimating renal function by investigating a sample including a large proportion of frail older people.
- Carnevale V.
- Tinti M.G.
- Scillitani A.
- Nieddu L.
Estimate glomerular filtration rate and muscle mass: Their relationship in older inpatients.
J Am Med Dir Assoc. 2019; 20: 1469-1471
2We believe that this could partly depend on the age-composition of different samples generating such equations, which in turn may reflect differently the age-related decay of skeletal muscle mass. Interestingly, Dharmarajan et al found that the Cockcroft-Gault formula (C-G) provided worse estimate of kidney function than Modification of Diet in Renal Disease and Chronic Kidney Disease Epidemiology Collaboration equations in patients aged ≥70 years. In our opinion, the latter result should be handled with care. The National Kidney Foundation recommends against the clinical use of C-G because it was generated before standardized creatinine assays were available. C-G estimates creatinine clearance (CrCl) rather than glomerular filtration rate. CrCl is in turn affected by proximal tubular secretion of creatinine
- Dharmarajan T.S.
- Yoo J.
- Russell R.O.
- Norkus E.P.
Chronic kidney disease staging in nursing home and community older adults: Does the choice of Cockcroft-Gault, Modification of Diet in Renal Disease Study, or Chronic Kidney Disease Epidemiology Collaboration Initiative equations matter?.
J Am Med Dir Assoc. 2012; 13: 151-155
3and the decline of renal function is associated with an augmented contribution of tubular creatinine secretion to the total CrCl by the residual nephrons.
- Stevens L.A.
- Coresh J.
- Greene T.
- Levey A.S.
Assessing kidney function-measure and estimated glomerular filtration rate.
N Engl J Med. 2006; 154: 2473-2483
4Moreover, weight being equal, lean mass decreases and fat mass increases with aging, so that the C-G (only including weight) may also suffer some inaccuracy arising from the age-related changes of body composition. In conclusion, we strongly agree with the final remark of the authors that glomerular filtration rate progression should always be estimated the same way in each patient to reliably compare the results. This seems quite trivial but reflects the real world clinical experience of the authors.
- Ellam T.
Increased tubular creatinine secretion by remnant nephrons-unexplained but informative?.
NDT Plus. 2011; 4: 138-139
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- Estimate glomerular filtration rate and muscle mass: Their relationship in older inpatients.J Am Med Dir Assoc. 2019; 20: 1469-1471
- Chronic kidney disease staging in nursing home and community older adults: Does the choice of Cockcroft-Gault, Modification of Diet in Renal Disease Study, or Chronic Kidney Disease Epidemiology Collaboration Initiative equations matter?.J Am Med Dir Assoc. 2012; 13: 151-155
- Assessing kidney function-measure and estimated glomerular filtration rate.N Engl J Med. 2006; 154: 2473-2483
- Increased tubular creatinine secretion by remnant nephrons-unexplained but informative?.NDT Plus. 2011; 4: 138-139
© 2020 Published by Elsevier Inc. on behalf of AMDA - The Society for Post-Acute and Long-Term Care Medicine.
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- Estimated Glomerular Filtration Rate and Muscle Mass in Older Patients: Diagnostic Accuracy of Creatinine-Based Equations and Implications in PracticeJournal of the American Medical Directors AssociationVol. 21Issue 4
- PreviewThe study by Carnevale et al compared the different methods used to measure estimated glomerular filtration rate (eGFR) with the estimated total skeletal muscle mass (eTSMM) and highlighted the high degree of variability.1 The decline in muscle mass or sarcopenia that occurs with aging renders the value of serum creatinine as a poor estimate of eGFR, especially in the frail old, a fact demonstrated decades ago.2 In particular, the modification of diet in renal disease (MDRD) study included only a limited number of older adults, as acknowledged by the authors, in a comparison of the MDRD formula with the Cockcroft-Gault (C-G) formula and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations; the lack of concurrence or divergence of eGFR values while using these formulae poses limitations when they are applied specifically in older adults.