Dialysis dose and gender: A different hypothesis

Abstract

To the Editor: A recent report1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar suggested that females who are smaller than males need higher dialysis dose (Kt/V) than males. The idea that smaller persons require higher Kt per L of V is not new2.Lowrie E.G. Li Z. Ofsthun N. Lazarus J.M. Body size, dialysis dose and death risk relationships among hemodialysis patients.Kidney Int. 2002; 62: 1891-1897Google Scholar, and suggests that a 0-intercept rule for judging Kt per unit of V is incorrect3.Lowrie E.G. Letter to the editor.Kidney Int. 2003; 63: 1962Google Scholar. Figure 1 illustrates a non-0 intercept rule (thick black line: Kt = 30 + 0.5 V)3.Lowrie E.G. Letter to the editor.Kidney Int. 2003; 63: 1962Google Scholar. The mean Kt ± SD (Table 3)1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar is shown for females (squares) and males (circles) at the mean V (Table 2)1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar for the high (upper symbols) and low (lower symbols) hemodialysis (HEMO) treatment groups. The steep, thin black line is a 0-intercept Kt/V rule (Kt = 0 + 1.16 V)1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar. All groups were treated at or above the Kt for their V by that rule. Females in the low treatment group (Kt = 38.2; eKt/V = 1.17), however, had marginally worse (P = 0.02) survival than females in the high treatment group1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar. The gray line (Kt = 35 + 0.3 V) is a rotation of the earlier black line3.Lowrie E.G. Letter to the editor.Kidney Int. 2003; 63: 1962Google Scholar, and better discriminates among groups according to outcome. Only low Kt/V females received substantially suboptimal therapy according to this illustrative rule. The point of this exercise was not to recommend a new rule for judging treatment. It only shows that one need not resort to speculations about different uremic toxin generation in males and females1.Depner T. Daugirdas J. Greene T. et al.Dialysis dose and the effect of gender and body size on outcome in the HEMO study.Kidney Int. 2004; 65: 1386-1394Google Scholar to explain this marginal survival difference. All one needs to do is accept the possibility that a 0-intercept Kt/V rule may be suboptimal.