Main findings and interpretation
Urodynamics appears to influence treatment decisions made by clinicians and patients in determining treatment pathways in women presenting with OAB. Women with DO were three times more likely to have had bladder relaxants than no treatment than women with a normal diagnosis. This could be interpreted as those who were shown to have DO either received prescribed bladder relaxant tablets more or patient compliance with taking the treatment was better. Women with a diagnosis of DO plus USI were 15 times more likely to have USI surgery than no treatment, which may at least partly explain the improved ICIQ scores and PGI-I in this group compared with the pure DO group.
A multicentre randomised double-blind trial (RCT) to determine whether women with or without a UDS finding of DO responded differently to antimuscarinic treatment demonstrated that UDS status was unable to predict treatment outcomes in women treated with the antimuscarinic agents or placebo . The objective in a recent Cochrane systematic review  was to determine if treatment according to UDS-based diagnosis compared with treatment based on history and examination alone led to more effective clinical care and better clinical outcomes in women with urinary incontinence. Two of the included trials [16, 17] demonstrated that women who underwent UDS were more likely to receive drugs to treat their symptoms than who did not (45% vs 21%, RR 2.09, 95% CI 1.32–3.31). Furthermore, three trials [18,19,20] found that those who had UDS were more likely to have their management changed (17% vs 3%, RR 5.07, 95% CI 1.87–13.74), although in five trials [16,17,18,19, 21], it was found that women were not more likely to undergo surgery after UDS (81% vs 79% RR 0.99, 95%CI 0.88–1.12). The evidence for the included surgical trials was of moderate quality (based on GRADE outcomes). Contrary to the findings of the Cochrane systematic review, we found that more women with DO plus USI diagnosis had received surgery by 20 months’ follow-up compared with those with a normal UDS diagnosis. Confirmation of the concurrent pathophysiology of DO plus USI may have resulted in the more clinicians offering USI surgery after suboptimal improvement with bladder relaxants alone.
In the overall population at 20 months, just over half the women (53%) reported long-term improvement in symptoms and ICIQ scores were reduced from baseline by 2.2 points (p < 0.001) on average, a difference that appears to be clinically meaningful. However, women treated with medical or surgical interventions based on UDS diagnoses appear to have greater reductions in symptoms than those who were not (57% vs 45%; p = 0.02). ICIQ scores were reduced at both time points regardless of whether the women received a treatment concordant with UDS findings or not, although patients receiving a concordant treatment reported a slightly greater reduction (−0.5 points; p = 0.02). The improvement reported by those who did not receive a concordant treatment could be for several reasons, such as the natural fluctuation of the disease state, regression to the mean and Hawthorne effect (individuals modify an aspect of their behaviour as a response to their awareness of being observed) . The experience of UDS may have helped women to understand their condition better and to improve compliance with lifestyle measures and medications.
Strengths and limitations
This study is one of the few reporting on the prospective follow-up in women with urgency and urge-predominant MUI and reporting better outcomes in the MUI group in comparison to the DO group. The response rate for continued follow-up of the cohort was 69% at 20 months; although not high, it is superior to other studies in the field. We captured the opportunity to assess the prognostic value of UDS and the outcomes following urodynamic diagnoses. The patients were followed up for more than 12 months and validated questionnaires were used. We believe that these data will hopefully offer some evidence to the clinical community that UDS does change patient management in current clinical practice.
The major limitation of this study is that it is not a randomized controlled trial (RCT) of outcomes based on treatment given to those with or without DO. Our results are therefore subject to unknown confounders, which may bias our results, including decisions to treat being based on information from sources other than UDS. Also, we could only ascertain whether women had “ever” having taken bladder relaxants as opposed to women currently taking bladder relaxants. Second, the number of women having both bladder relaxants and surgery was small, and therefore could not be reliably distinguished from those who had surgery alone. In addition, we did not collect data on therapies such as supervised intensive pelvic floor muscle training, bladder retraining, lifestyle changes etc., but we presumed that the conservative treatment was already exhausted before patients were referred for UDS. A further limitation was that we did not link information on HRT use with urodynamic diagnoses. Lack of oestrogen following the menopause is known to cause atrophic changes, which may be associated with lower urinary tract symptoms .
The response rate was 69%, in spite of sending reminder questionnaires, emails and telephone calls to improve this yield. Although we have no reason to suspect that patients with missing responses were any different from those who responded to questionnaires we cannot rule out that this may have affected our conclusions to an unknown degree.