What is important in dialysis? Efficiency: blood flow, KoA and Kt/V?

The relationships of clinical outcome to Kt/V and treatment time (t) in the two large randomized controlled trials of dialysis (National Cooperative Dialysis Study, NCDS, and the Hemodialysis Study, HEMO) were reviewed and compared to several major observational studies (OS). The HEMO study was originally conceived to determine whether outcome was improved by increasing Kt/V to 1.40, 40% higher than spKt/V >1.00 which was concluded to be adequate in the NCDS. However, OS suggested improvement in outcome up to and higher than Kt/V 1.40, so the HEMO dose targets were changed to 1.40 and 1.70. HEMO showed there was no change in outcome over this dose range but when the data were analyzed as a dose targeting OS, there was spurious improvement in outcome over the total range studied. Thus it cannot be concluded that Kt/V >1.0 results in improvement in clinical outcome since the range 1.00-1.40 has not been studied and both levels found adequate in randomized controlled trials. The borderline inverse correlation of outcome to treatment time in NCDS was shown to be meaningless because Kt/V was not successfully separated from t.