Mixed incontinence: the misclassification of patients and limitations of clinical trials.

Mixed urinary incontinence (MUI) has become a diagnosis of increased interest in the fields of urology and urogynecology, as drugs and treatments targeting urgency-related and stress-related symptoms are being developed and evaluated. We think the concept of "mixed incontinence" warrants revisiting because confounding clinical conditions exist, which result in a heterogeneous population of patients receiving the same diagnosis. The classification system for patients with signs and symptoms of MUI should undergo refinement. In addition, clinical trials for MUI should clearly delineate the lower urinary tract signs and symptoms found in the study population. Current study outcomes do not apply to the entire mix of patients included under the diagnosis of MUI, thus limiting their value. Investigation into the pathophysiologic basis of MUI and refinement of the definition of MUI are necessary if we are to evaluate the effect of future treatments on stress and urge components.