Selectivity of peak versus average male urinary flow rates.

Multiple peak and average urinary flow rates were measured in 34 normal men. In addition, this population was compared to 114 patients with prostatic obstruction. No matter which flow rate measurement is used some overlap is present between the 2 populations. The sensitivity of the flow rate test was defined for the 90 or 95 per cent limit of each normal and abnormal population. The specificity of both tests also was statistically determined. The ability to separate abnormal from normal voiding is enhanced significantly if peak flow rate is the measurement made. The loss of specificity for average flow rate is owing to a greater percentage of both populations, normal or abnormal, within the overlap region between the 2.