Solute removal index correlates more with equilibrated Kt/V than with single pool Kt/V in haemodialysis patients

Background and Aims: Solute removal index (SRI) is an adequacy index that estimates haemodialysis dose based on urea removal in the spent dialysate. We examined the SRI, single pool Kt/V (spKt/V) and equilibrated Kt/V (eKt/V) in two groups of chronic haemodialysis patients; group A, 25 patients received haemodialysis twice weekly and group B, 11 patients received haemodialysis thrice weekly. Method and Results: The Ing's partial dialysate collection method was used for spent dialysate collection. The SRI values of the first and second dialysis sessions in a week in group A were 68.7 +/- 4.7 and 69.7 +/- 4.1%, respectively, while that of the first, mid-week and third dialysis sessions in a week in group B were 56.5 +/- 5.3, 55.8 +/- 5.4 and 57.5 +/- 6.2%, respectively. The correlation coefficients (r) between SRI and spKt/V in the first and second dialysis sessions in a week in group A were 0.90 (P < 0.01) and 0.95 (P < 0.01), respectively, and that in the first, mid-week and third sessions for group B were 0.96 (P < 0.01), 0.94 (P < 0.01) and 0.91 (P < 0.01), respectively. The r values between SRI and eKt/V in the first and second sessions for group A were 0.97 (P < 0.01) and 0.99 (P < 0.01), respectively, and that in the first, mid-week and third sessions for group B were 0.98 (P < 0.01), 0.97 (P < 0.01) and 0.98 (P < 0.01), respectively. Therefore, the correlation between SRI and eKt/V (r values approaching one) was better than that between SRI and spKt/V in all dialysis sessions in a week for both group A and B patients. Conclusion: We conclude that the SRI, an index based on dialysate urea removal, correlates more with equilibrated Kt/V (an index that accounted for postdialysis urea rebound) than with single pool Kt/V.