BACKGROUND: Overactive bladder is a common problem affecting women worldwide, with a negative effect on their social and professional lives. Before considering invasive treatments, guidelines recommend urodynamics to identify detrusor overactivity. However, the clinical-effectiveness and cost-effectiveness of urodynamics has never been robustly assessed in this cohort of women. We aimed to compare the clinical-effectiveness and cost-effectiveness of urodynamics plus comprehensive clinical assessment (CCA) versus CCA only in the management of women with refractory overactive bladder symptoms. METHODS: We did a multicentre, superiority, parallel, open-label, randomised controlled trial in 63 UK hospitals. Women aged 18 years or older with refractory overactive bladder or urgency predominant mixed urinary incontinence, with failed conservative management and being considered for invasive treatment, were randomly assigned (1:1) to urodynamics plus CCA versus CCA only. Assignment used an internet-based application with stratified random permuted blocks and site and baseline diagnosis as stratum. Primary outcome was participant-reported success at the last follow-up timepoint, measured by the Patient Global Impression of Improvement at 15 months after randomisation. Primary economic outcome was incremental cost per quality-adjusted life-year (QALY) gained modelled over the participants lifetime. Analysis was based on the intention-to-treat principle. This study is registered with ISRCTN registry (ISRCTN63268739). FINDINGS: Between Nov 6, 2017, and March 1, 2021, 1099 participants were randomly assigned to urodynamics plus CCA (n=550) or CCA only (n=549). At the final follow-up timepoint, participant-reported success rates of "very much improved" and "much improved" were not superior in the urodynamics plus CCA group (117 [23·6%] of 496) versus the CCA-only group (114 [22·7%] of 503
adjusted odds ratio 1·12 [95% CI 0·73-1·74]
p=0·60). Serious adverse events were low and similar between groups. Incremental cost-effectiveness ratio was £42 643 per QALY gained. The cost-effectiveness acceptability curve showed urodynamics had a 34% probability of being cost-effective at a willingness-to-pay threshold of £20 000 per QALY gained, which reduced further when extrapolated over the patient's lifetime. INTERPRETATION: In women with refractory overactive bladder or urgency predominant mixed urinary incontinence, the participant-reported success in the urodynamics plus CCA group was not superior to the CCA-only group, and urodynamics was not cost-effective at the £20 000 per QALY gained threshold. FUNDING: UK National Institute for Health and Care Research Health Technology Assessment Programme.