NICE guidelines 2018, currently out to consultation, suggest that urodynamic assessment is NOT required in women with stress predominant mixed urinary incontinence (MUI) prior to surgical intervention. This is based predominantly on expert opinion, as data on this topic is sparse. We have assessed the predictive power of the predominant symptom of MUI to determine the underlying urodynamic abnormalities to further clarify this issue.

Over a 4-month period from June to September 2018, 35 women with a mean age of 55years (range 26-86) with MUI attended for video-urodynamic studies (VUDS). They were asked a predefined set of questions aimed at assessing the predominant symptomatic component of their incontinence. Immediately following the questionnaire, VUDS were performed in accordance with ICS guidance.
Statistical analysis was by Chi Squared analysis and analysis of sensitivity, specificity, positive and negative predictive values.

22(63%) women described the urge component as most bothersome, 10(28%) the stress component and 3(9%) felt both components were equally bothersome. Outcomes of their video-urodynamics are detailed in Table 1.Combined stress and overactivity leakage was demonstrated in only 10 (28%).  
The sensitivity and specificity of symptomatic stress urinary incontinence (SUI) for urodynamic finding of stress urinary incontinence (USUI) were 43% and 91% respectively. The sensitivity and specificity of symptomatic urge urinary incontinence (UUI) for the finding of detrusor overactivity (DO) incontinence were 77% and 43%.
The positive predictive value of SUI for USUI was 90% whilst the negative predictive value was only 45%. The positive predictive value for UUI for DO was 64% and the negative predictive value was 60%.

Symptomatic SUI is predictive of USUI in women with MUI in 90% however concurrent DO is missed in 40%. Symptomatic UUI is predictive of DO in 64% and USUI is missed in 55%.

These preliminary results indicate that patient perception of symptoms is insufficient to guide invasive treatments and urodynamics are required to delineate the physio-pathological mechanisms of incontinence and accurately guide treatment.