Introduction: There are several shortcut formulas to calculate Kt/V, the mo
st widely used because of its simplicity is the logarithmic formula propose
d by Lowrie in 1983. The DOQI report recommends use of the formula proposed
by Daugirdas's in 1993 to estimate the Kt/V, it must be greater than or eq
ual to 1.2. The aim of the present work was to analyse the concordance betw
een the second generation Daugirdas's formula and the other shortcut formul
as.
Material and metods: In 208 hemodialysis sessions performed on 61 patients,
Kt/V was estimated by thirteen formulas: 10 single-pool modeling and three
double-pool modeling.
Results: The Kt/V values obtained by Daugirdas's formula was different from
those obtained with the other single-pool based formulas (p < 0.01). When
the dialysis sessions were classified in 4 groups according to the Kt/V val
ues calculated by Daugirdas's formula, most of the single-pool formulas gav
e Kt/V values statistically different from those given by Daugirda's formul
a in all ranges examined. The concordance among Kt/V calculated by every on
e of the single-pool formulas and Daugirdas's formula was variable. The hig
hest agreement was with Keshaviah's and Lowrie's 1992 formulas and the lowe
st with Calzavare's and Lowrie's 1983 formulas. The linear multivariate ana
lysis showed that the two factors which influenced the concordance were the
Kt/V value obtained by the Daugirdas's formula, and the quotient between t
he postdialysis body weight and the ultrafiltration rate.
Despite the weak concordance with Daugirdas's formula, the Kt/V obtained by
Lowrie's 1983 formula and the urea reduction ratio (URR) are still useful
tools to monitor the adequacy of dialysis: a Kt/V > 1.065 calculated by the
Lowrie's 1983 formula and a PRV > 65% are equivalent to a Kt/V greater tha
n or equal to 1.2 calculated by Daugirdas's formula.
Conclusions: The shortcut formulas used to calculate Kt/V give different re
sults with high intermethod variability. When Kt/V is reported it is absolu
tely necessary to indicate the formula used to calculate it. The Kt/V obtai
ned by Lowrie's 1983 formula and the URR are useful tools to monitor dialys
is adequancy.