VARIABILITY IN URINARY FLOW-RATE AND PROSTATE VOLUME - AN INVESTIGATION USING THE PLACEBO ARM OF A DRUG TRIAL

Purpose: We analyzed a large data set to study reproducibility of peak urinary flow rates and prostate volumes in benign prostatic hyperplas ia patients. Materials and Methods: Longitudinal data were analyzed fr om 284 placebo treated patients in a double-blind, placebo controlled benign prostatic hyperplasia drug trial. Results: A statistically sign ificant increase in mean maximum flow rate was seen in the initial 3 m easurements, as well as after adjusting for voided volume and time bet ween uroflows. The mean maximum flow rate increased from 8.61 to 9.36 ml. per second at measurement 4 (8.7%). Of the patients 43% had 2 cons ecutive prostate volume determinations within +/- 10%. Within patient variability accounted for 7% of total prostate volume variability. Con clusions: With subsequent voidings maximum flow rate increases in a la rge group of patients. At least 4 uroflows must be performed to reach a plateau for maximum flow rate. Explanations for this finding may be the increasing experience of the patient and regression to the mean. T hese findings may impact on comparison of large trials of treatment ef ficacy. Within patient variability of prostate volume is substantial a nd, in addition to measurement method and lack of reader blinding to t ime and patient identity, may be caused by other yet unknown factors.