Annals of Oncology Advance Access originally published online on May 16, 2005
Annals of Oncology 2005 16(6):990; doi:10.1093/annonc/mdi174
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© 2005 European Society for Medical Oncology
Letter to the Editor |
Reply to the letter "Limitations of bedside estimates of renal function", by M. J. Dooley and S. G. Poole (doi:10.1093/annonc/mdi173)
It is with interest that we read the letter by Dooley and Poole [1
]. As expected with any surrogate measure of renal function evaluation, there are limitations. This is particularly so when evaluating renal function using creatinine as a variable. As renal function declines there is an increase in the active tubular secretion of creatinine. This results in reduced accuracy and precision in the lower renal function range. Our study demonstrates that in the range of glomerular filtration rate (GFR) from 50–120 ml/min the Wright formula [2] is the most accurate and precise estimate of renal function [3]. We have reported the degree of bias that can be expected within a particular range of GFR. This provides clinicians with an expected degree of variation within various ranges of GFR. Provided that the degree of variation is acceptable for the particular clinical situation, this estimate would be a reasonable estimate of renal function. The clinical appropriateness would be based on treatment goals, disease state and chemotherapy agent. If the degree of variation is not acceptable for the particular situation then the clinician would need, at this stage, to continue to use EDTA or DTPA GFR measures. We specifically did not include the lower range of GFR in our conclusions as accuracy and precision in this range is limited. Our results were similar to those described by Poole et al. [4], with an overestimation seen with the Wright formula in the lower GFR range. We agree that this group of patients is of particular interest for the development of reliable formulae that estimate renal function. At this stage, however, the data suggest that all available formulae have limitations in renal function estimation in the lower range of renal function, and these patients should continue to rely on Tc99m DTPA and C51 EDTA measurements. In the higher range of GFR, provided that the degree of bias is acceptable for the clinical situation, these expensive and often unavailable tests may be avoided. Ongoing research to provide more accurate estimates across the whole range of GFR is still required.
1 Sydney Haematology Oncology Clinic, Sydney, NSW; 2 Border Medical Oncology, Wodonga, Victoria; 3 Guy's Hospital, London, UK
Email: gmarx{at}shoc.com.au.
References
1. Dooley MJ, Poole SG. Limitations of bedside estimates of renal function. Ann Oncol 2005; 16: 990.
2. Wright JG, Boddy AV, Highley M et al. Estimation of glomerular filtration rate in cancerpatients. Br J Cancer 2001; 84: 452–459.[CrossRef][Web of Science][Medline]
3. Marx GM, Blake GM, Steer CB et al. Evaluation of the Cockcroft-Gault, Jelliffe and Wright formulae in estimating renal function in elderly cancer patients. Ann Oncol 2004; 15: 291–295.
4. Poole SG, Dooley MJ, Rischin D. A comparison of beside renal function estimates andmeasured glomerular filtration rate (Tc99m DTPA clearance) in cancer patients. Ann Oncol 2002; 13: 949–955.
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  G. M. Marx, C. B. Steer, and P. G. Harper Reply to the letter "Limitations of bedside estimates of renal function", by M. J. Dooley and S. G. Poole (doi:10.1093/annonc/mdi173) Ann. Onc., June 1, 2005; 16(6): 990 - 990. [Full Text] [PDF]
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