NDT Advance Access originally published online on August 25, 2006
Nephrology Dialysis Transplantation 2006 21(12):3488-3494; doi:10.1093/ndt/gfl430
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The relationship between estimated glomerular filtration rate, demographic and anthropometric variables is mediated by muscle mass in non-diabetic patients with chronic kidney disease
1School of Sport, Health and Exercise Sciences, University of Wales, Bangor, George Building, Bangor, Gwynedd LL57 2PZ, 2Renal Unit, Ysbyty Glan Clwyd, Rhyl, Denbighshire LL18 5UJ, 3Renal Unit, Ysbyty Gwynedd Penrhosgarnedd, Bangor, Gwynedd LL57 2PW and 4Department of Chemical Pathology and Metabolism, St Helier Hospital, Carshalton, Surrey SM5 1AA, UK
Correspondence and offprint requests to: Jamie Hugo Macdonald School of Sport, Health and Exercise Sciences, University of Wales, Bangor, George Building, Bangor, Gwynedd LL57 2PZ, UK. Email: j.h.macdonald{at}bangor.ac.uk
Background. In this study (the first of two related papers), we report whether the relationship between the demographic and anthropometric variables (DA, i.e. age, gender, height and weight) employed in current creatinin (Cr)-based glomerular filtration rate (GFR) estimation equations and actual GFR is mediated by muscle mass.
Methods. We studied 77 patients (mean age ± SD, 65.1 ± 11.9 years) with chronic kidney disease (mean GFR 45.7 ± 28.6 ml/min/1.73 m2). Actual GFR was measured by the renal clearance of inulin (GFRinu). Appendicular lean mass (ALM) and its index (ALMI) by dual energy X-ray absorptiometry provided markers of muscle mass. Multiple regression analyses identified variables explaining variance in (i) GFR, (ii) ALM and (iii) Cr.
Results. (i) The DA variables used in the abbreviated modification of diet in renal disease (MDRD) equation accounted for only 59.6% (P < 0.001) of the variance in GFRinu, whilst adding ALMI explained an additional 10.4% variance (P < 0.001). If ALMI was entered first, the relationship between DA variables and GFRinu was reduced (for weight) or completely abolished (for age, gender and height). (ii) After inputting all the commonly used DA variables, 17.2% of the variance in ALM was unexplained. (iii) All the DA variables explained only 60.6% (P < 0.001) of the variance in Cr, whilst adding ALM explained an additional 4.2% variance (P < 0.005).
Conclusions. Muscle mass explained more variance in GFRinu than MDRD DA variables and mediated the relationship between GFRinu and DA variables. Furthermore, DA variables failed to account for individual differences in muscle mass or Cr. Consequently, there is a need to validate simpler, clinically obtainable measures of muscle mass and determine whether these measures will improve GFR estimation.
Keywords: chronic kidney disease; creatinine; DXA; glomerular filtration rate; MDRD; muscle mass
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NDT 2006 21: 3481-3487.[Abstract] [FREE Full Text]
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  J. H. Macdonald, S. M. Marcora, M. Jibani, G. Roberts, M. J. Kumwenda, R. Glover, J. Barron, and A. B. Lemmey Bioelectrical impedance can be used to predict muscle mass and hence improve estimation of glomerular filtration rate in non-diabetic patients with chronic kidney disease Nephrol. Dial. Transplant., December 1, 2006; 21(12): 3481 - 3487. [Abstract] [Full Text] [PDF]
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