Related Experiment Videos
Low reproducibility of maximum urinary flow rate determined by portable flowmetry
G S Sonke1, L A Kiemeney, A L Verbeek
1Center for Epidemiologic Urology, and Department of Epidemiology, University of Nijmegen, The Netherlands.
Neurourology and Urodynamics
|May 25, 1999
Summary
Obtaining a reliable maximum urinary flow rate (Qmax) in men with lower urinary tract symptoms requires approximately 25 flow measurements. Current urologic practice typically performs fewer, potentially impacting diagnostic accuracy.
Area of Science:
- Urology
- Medical Engineering
- Clinical Diagnostics
Background:
- Lower urinary tract symptoms (LUTSs) affect a significant number of men, often necessitating objective measures like maximum urinary flow rate (Qmax) for diagnosis and management.
- Reproducibility of Qmax measurements is crucial for accurate assessment of bladder outlet obstruction and treatment response.
- Current clinical practices may not provide sufficient data for reliable Qmax determination.
Purpose of the Study:
- To evaluate the reproducibility of maximum urinary flow rate (Qmax) measurements in men with LUTSs.
- To determine the optimal number of flow measurements needed to achieve a specified level of reliability for mean Qmax.
- To assess the impact of voided volume thresholds and potential learning curves on Qmax reproducibility.
Main Methods:
- 212 male patients with LUTSs underwent home-based uroflowmetry using a portable device, recording over 1,854 voiding events.
- Maximum flow rate (Qmax) and voided volume were measured, with analyses performed using different voided volume cutoffs (≥100 ml and ≥150 ml).
- Coefficient of variation (CV) was calculated for individual patients and pooled to estimate the number of flows required for reliable mean Qmax determination, with and without excluding initial flows to assess learning effects.
Main Results:
- The average number of valid flows per patient was nine, with a mean Qmax of 13.2 ml/sec and a mean CV of 24%.
- Approximately 25 flow measurements are estimated to be necessary to achieve a 10% deviation from the true mean Qmax.
- No significant learning curve effect was observed, and a single Qmax measurement has wide confidence interval boundaries (approx. 50% below or above).
Conclusions:
- Reliable determination of mean Qmax in men with LUTSs necessitates considerably more flow measurements than are typically performed in urologic practice.
- Current standard uroflowmetry protocols may lead to insufficient precision for accurate clinical decision-making.
- Further research into standardized, multi-measurement uroflowmetry protocols is warranted to improve diagnostic accuracy for LUTSs.