Flow measurements: Can several "Wrongs" make a "Right"?

Aims: Although measurement of maximum flow rate (Q(max)) is a standard and straightforward test, it is often difficult to obtain reliable readings. We obtained multiple measurements using a simple home uroflow device which categorizes Q(max) into ranges. We hypothesize that the average of a series of relatively coarse measurements of Q(max) would be more repeatable and therefore more representative of an individual's voiding function than a single, albeit more precise measurement. Methods: We studied 22 male volunteers with a wide range of Q(max). They were asked to record flow category (< 10 ml/sec; 10-15 ml/sec; 15-20 ml/sec; > 20 ml/sec) and voided volume twice daily for 12 days using the home flow device. in addition, a clinic-based flow recording using a spinning-disc uroflowmeter was obtained at both the start and the end of the 12-day period. Results: Good agreement between mean home flow and mean clinic flow was seen with mean (SD) difference of 1.3 (5) ml/sec. The mean for consecutive halves of an individual's home flow data showed excellent agreement (-0.2 (1.3) ml/sec). The two clinic readings showed poorer agreement (2.3 (6.8) ml/sec) than the home readings, and poorer agreement even than between clinic and home flows. Conclusions: Although simple in design, the home flowmeter actually shows greater accuracy than might be expected when used repeatedly to study the flow rates of men. Simple flow devices such as this could be used in conjunction with voiding diaries to give a more representative picture of patients' day-to-day voiding function.