Can the idealized voider derived flow indexes be a measure of voiding efficiency and how accurate are they?

OBJECTIVE: Our hypothesis was to confirm whether an idealized voider flow equation (IVFE) that we created is more accurate than trying to rely on estimated flow rates in the same patient in two consecutive voids. We also looked to confirm whether flow index (FI) can be a proxy for voiding efficiency and to identify which FI was best; those based off our own IVFE equations or those derived from the commonly used power equations.

STUDY DESIGN: We used data from a previous study and calculated flow rates using our IVFE and the power equations. Descriptive statistics and non-parametric tests were performed along with error analysis using Bland Altman (BA) and accuracy analysis (AA).

RESULTS: Bland Altman (BA) analysis revealed that flows obtained from normal voiders voiding between 100 and 200 cc as well as from 50 cc to 115% of EBC are comparable and tend to be reproducible in subsequent voids. FI derived from the IVFE exhibit less bias than Qmax making it a better way to compare these voids. A comparison of Qmax and flow index for different combinations of volumes and PVR's was done utilizing BA and accuracy measures both indicating that FI was more reproducible.

CONCLUSION: The data support both of our hypothesis that flow index is a good measure of voiding efficiency. We have also shown that IVFE is a better and more accurate measure of calculating a flow index than the power equations regardless of the volume and PVR scenarios that are presented.