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10:21 - 10:27
ICCS S4-2
(LO)
IS THERE A DIFFERENCE BETWEEN DIFFERENT QMAX FLOW INDEXES (FI,
ACTUAL Q/EST. Q)
Jacob FRANCO
1
, Stephen YANG
2
and Israel FRANCO
3
1) Stonybrook University Medical School, Urology, Chappaqua, USA - 2) Buddhist Tzu Chi University, Urology, New
Taipei,, TAIWAN - 3) New York Medical College, Section of Pediatric Urology, Chappaqua, USA
PURPOSE
There have been attempts to normalize uroflowmetry to volume by using a flow index. A recent report in the adult
literature indicates that Total bladder volume
0.5
(√TBV) is a good predictor of abnormal voiding. Our our own studies
using our own quadratic derived estimated Q indicates that this is a good way to evaluate patients objectively. We set
out to determine if there are differences between the different FI’s described and which is most accurate.
MATERIAL AND METHODS
A data set consisting of 1268 children who underwent 2 voids was used to test our sex specific formulas to derive FI
Q
max
. FI based off the voided volume
0.5
(√VV) and √TBV as well as Q
max
with our formula using VV instead of TBV. FI
for each void were compared and tested for accuracy. Non-parametric testing was done on the different groups to
confirm no difference from the first to the second void.
RESULTS
We found that for both sexes that FI using our derived formulas were more accurate and approached unity (0.96, 0.93
females and males) while FI= √VV=1.7, 1.6 and FI √TBC= 1.7, 1.6. We saw little difference when we used our
normalized FI with VV except in cases of elevated PVR where it can then influence the FI and reduce accuracy. √MSE
were 0.28, 0.29,0.35,0.36 and 0.28,0.28,0.52,0.53 repestectively for males and females for bell normalized FI TBV and
VV, √VV, √TBV.
CONCLUSIONS
The old standard of using √VV as a measure of the expected Q
max
leaves a wide margin for error. This concept needs to
be discarded and replaced with a more accurate predictor of expected flow, a FI based on an idealized normal voider
derived quadratic formula which estimates Q
max
and accounts for residual urine and the slowing of the stream at high
volumes seems to be the most accurate method.