Estimation of the Kt/V with a ionic dialysance monitor

The Diascan equipment (Hospal) measures ionic dialysance from which it deri ves the Kt/V It is automatic, does not need blood samples and displays the results in real time. The aim of the present study was to compare the Diasc an Kt/V with the Kt/V obtained with four simple formulas: two based on a si ngle pool model of urea kinetics (Lowrie 1983 and Daugirdas 1993) and the o ther based on the two pool model (Maduell formulation applied to Lowrie Kt/ V and that proposed by Daugirdas 1995). We have analyzed the inter-method variability, the degree of relationship a mong the different procedures for Kt/V calculation and the intra-individual variability. The intermethod variability between Kt/V Diascan and Kt/V cal culated by the four simple formulas were studied in one hemodialysis sessio n in 19 patients. The Kt/V Diascan was statistically different from that ca lculated by the four formulas (1,021 +/- 0.140 Diascan vs 1.147 +/- 0. 124 for Lowrie-83; vs 1.373 +/- 0.164 for Daugirdas-93; vs 0.963 +/- 0.105 for Maduell and vs 1.173 +/- 0.143 for Daugirdas-95, p < 0.01). The lowest inte r-method variability was obtained with the Maduell's Kt/V (relative differe nce 9%) but even in this case 37% of patients had a variability above 10%. The correlation coefficient was not high enough to allow an estimation of t he different Kt/V measurements from the Diascan Kt/V by a regression equati on. To study the individual relationship between the Diascan Kt/V and the Kt/V calculated by the four formulations, we have determined the Kt/V every 30 m inutes in one hemodialysis session in 30 patients. In all patients we obser ved a good relationship between the Diascan Kt/V and the other four (correl ation coefficient of 0.9952 for Lowrie-83, 0.9976 for Daugirdas-93, 0.9961 for Maduell and 0.9971 for Daugirdas-95); with these correlation coefficien tes it was possible to derive regression equations and to obtain an estimat ion of the four Kt/V's from the Diascan Kt/V. To study the individual variability of each procedure used in the Kt/V calc ulations we determined the coefficient of variation of the different method s in 5 consecutive hemodialysis sessions performed under identical conditio ns in 19 patients. The coefficient of variation was 3.7 <plus/minus> 1.8% f or the Diascan K/V; 6.0 +/- 2.8 for the Lowrie-83 Kt/V 5.8 +/- 2.4 for the Daugirdas-93 Kt/V 6.5 +/- 2.6% for the Maduell Kt/V and 5.7 +/- 2.2% for th e Daugirdas-95 Kt/V (p < 0.01 between the Diascan Kt/V and the other four). Conclusions: Although the Diascan Kt/V was statistically different from the other four Kt/V's calculated by the usual formulas, the Diascan Kt/V has a n excellent correlation with all of them and showed a lower intra-individua l variability. It is possible to obtain an estimation of the calculated Kt/ V for each patient by linear regression equation.