Overactive bladder
Definition and prevalence
Overactive bladder (OAB) is defined by the International Continence Society and the International Urogynaecology Association1 as a symptom complex of urinary urgency (an intense, sudden desire to void) with or without incontinence, usually with increased urinary frequency or nocturia, but in the absence of infection or other proven pathology. Increased urinary frequency and urgency seem to be more common symptoms of OAB than urinary incontinence (UI). Incontinence may be the most distressing symptom of OAB, but affects only one-third of patients.2
Overactive bladder affects millions of people worldwide. In the epiLUTS study, OAB prevalence was found to be 12.8%.3,4 Prevalence and severity of OAB are known to increase with age from 14.9% in the 18- to 29-year group, to 21.3% in the 30- to 39-year group, 32.9% in the 40- to 49-year group, 35.8% in the 50- to 59-year group and up to 39.8% in the 60- to 69-year group.5 With the increase in longevity owing to advances in health care and the population growth, the burden of OAB is going to increase in the next few decades, with a 9% increase anticipated from 500 million globally in 2013 to 546 million by 2018.6 Two-thirds of a predominantly female sample of people with OAB had sought treatment in the 6 months prior to a multinational survey.7
Moderate-to-severe symptoms may have an adverse impact on lifestyle. Affected women tend to cope by restricting fluid intake and ‘toilet mapping’ to control urgency and frequency.8 Women may avoid sexual contact because of the risk of coital incontinence.9 These coping strategies can have a deleterious effect on physical, social and emotional health. Low mood and depression due to social restriction and fear of embarrassment are also associated with OAB in women (with and without urgency incontinence), while OAB also has significant financial implications (e.g. cost of pads, prescriptions, time off work, job losses, effects on the family, etc.).10,11 Urgency or nocturia in the elderly have been linked to a higher risk of falls and fractures.12
Mixed urinary incontinence
The International Continence Society and International Urogynecology Association describe mixed urinary incontinence (MUI) as a complaint of involuntary loss of urine associated with urgency and also with effort or physical exertion, or on sneezing or coughing.1 MUI may be urgency-predominant or stress-predominant and accounts for 49% of UI in women.13 In a study on the prevalence of individual symptoms of MUI, 29% of participants had stress-predominant MUI, 15% of participants had urgency-predominant MUI and 56% (912/1626) of participants had equal severity of urgency- and stress-related MUI.13 Appropriate categorisation of women into urgency-predominant or stress-predominant MUI has been a matter of great debate. Previous studies have used the Medical, Epidemiological, and Social Aspects of Ageing (MESA) Questionnaire,14 the Urogenital Distress (UI) Inventory15 and visual analogue scale (VAS) scores alongside 7-day bladder diaries to categorise women with mixed incontinence based on the predominant symptom (stress or urgency).16 However, in routine clinical practice, women are categorised based on which symptoms they consider are more bothersome.
Underlying pathology of overactive bladder
The pathology behind OAB symptoms has been found to be detrusor overactivity (DO) in 54–58% of the cases. The remaining 42–46% of the patients may have other pathologies causing OAB symptoms17 ().
Conditions that cause OAB
The pathophysiology of the DO and other causes of OAB have not been understood completely. Enhanced afferent activity generated by the detrusor smooth muscle and the urothelium/lamina propria may be the main mechanism.18 In vitro studies have shown that spontaneous contractile activity was seen more often in muscle strips from overactive than from normal bladders.19
According to the myogenic theory, DO may be caused by an intrinsic abnormality of the detrusor muscle rather than a disturbance of its neural control. Detrusor smooth muscle cells may become hyperexcitable, react to minor stimuli and result in untimely bladder contractions resulting in urgency. In isolated bladder preparations from patients with DO, there seems to be increased co-ordination leading to larger amplitude contractions, possibly reflecting changes in intercellular communication.20
In OAB patients, increase in intravesical pressure secondary to detrusor contractions may cause the symptom of urgency and prompt the woman to increase her urethral closure pressure using her urethral sphincter and pelvic floor musculature. Such isometric contractions against a closed bladder neck and competent sphincter may lead to the hypertrophy of the detrusor. A thickened bladder wall is suggestive of detrusor hypertrophy.21
Clinical history
Clinical history taking for urinary symptoms includes the type of incontinence (provoked by urgency or activity), duration and severity of symptoms, impact of symptoms on quality of life (QoL), exacerbating factors including diet, fluid and medications, co-existing medical, surgical or gynaecological conditions and the person’s strategies for coping with symptoms. In a semisystematic review, mean sensitivity and specificity of clinical history compared with a reference standard diagnosis made by urodynamics (UDS) was 69% (range 35–96%) and 60% (range 21–97%), respectively, for OAB, and 51% (range 38–84%) and 66% (range 43–96%), respectively, for women with MUI.22 Mean sensitivity for predicting DO in women with clinical symptoms of OAB was 76%, but the specificity was only 57%.22 Meta-analytical averages were not presented.
However, in a more methodologically thorough review, Martin et al.23 reported the pooled sensitivity of clinical history assessment of urgency symptoms, compared with a UDS diagnosis of DO, to be lower at 61% [95% confidence interval (CI) 57% to 65%], and the specificity to be higher at 87% (95% CI 85% to 89%).
History of urinary symptoms alone may not help in the differentiation of the underlying pathology.24,25 Women go through a thorough clinical assessment to rule out other causes of OAB, for example urogenital atrophy, significant pelvic organ prolapse (POP), and should undergo post-void residual (PVR) ultrasonography to rule out incomplete bladder emptying.
Bladder diaries in the assessment of overactive bladder
Bladder diaries are useful tools in the investigation of lower urinary tract symptoms (LUTS)3 and also to assess treatment response.26 Episodes of urgency and sensation may also be recorded, along with the activities performed during or immediately preceding the involuntary loss of urine. Severity of incontinence in terms of leakage episodes and pad use may also be reported in bladder diaries. On evaluation of accuracy of bladder diaries in OAB patients against the urodynamic diagnosis of DO, sensitivity and specificity were found to be 0.88 and 0.83, respectively.27 A high subjective score of urgency, frequent voiding and urgency incontinence episodes (over a 3-day diary period) were strongly associated with urodynamic DO in a multivariate analysis.28
Urodynamics
Urodynamics are used to assess the neuromuscular function of the urinary tract and understand its storage and evacuation.29 There are two basic aims of the UDS test: (1) to reproduce the patient’s symptoms and (2) to provide a pathophysiological explanation for the patient’s problems.2 At present, laboratory UDS remain the gold standard test for assessment of OAB. Multiple diagnoses can be given following UDS tests, which include DO, urodynamic stress incontinence (USI), a combination of DO and USI and voiding dysfunction (VD).
Urodynamics consists of uroflowmetry, which measures the flow rate during voiding, and multichannel cystometry, which evaluates the pressure–volume relationship in the bladder during both filling and voiding phases. It is usually performed in the sitting or supine position and takes approximately 30 minutes to perform. Ambulatory UDS utilises natural filling and provides a more physiological technique for continuous monitoring of bladder function under nearly natural conditions, but does require a longer period of observation and for the patient to carry a data storage device while catheterised. Standard multichannel UDS has a NHS tariff of £401.30 There were approximately 39,792 UDS attendances in England and Wales in 2013,31 although there is a 23-fold variation in uptake between localities.32
Detrusor overactivity and low compliance are urodynamic diagnoses. DO is the occurrence of involuntary detrusor contractions during the filling phase of UDS. These contractions, which may be spontaneous or provoked, produce a wave form on the cystometrogram of variable duration and amplitude.33 Neurogenic DO is where there is DO and there is evidence of a relevant neurological disorder.33 In a normal compliant bladder, the bladder accommodates large volumes without a significant rise in detrusor pressure, but if the elasticity of the bladder is reduced, pressure rises with filling and the bladder is said to have low compliance.
In women with OAB symptoms, 45% do not have a diagnosis DO on UDS. UDS may miss DO if DO is not present at all times during the filling phase, or because UDS is not a test mimicking normal physiology and hence is not able to capture DO at its occurrence.34 In a study of 2737 women with UI symptoms, 1626 (59%) reported mixed UI, of whom 42% had USI, 25% had pure DO, 18% had both DO and USI and 15% had normal UDS.35 In those with stress-predominant MUI, 64% had pure USI and in those with urgency-predominant MUI, only 47% had solely DO.35
Clinical use of urodynamics
National Institute for Health and Care Excellence (NICE) guidelines (CG 171)36 advise against the use of multichannel, ambulatory UDS or video UDS prior to commencing conservative management for OABs. However, there are recommendations to perform UDS before proceeding to invasive treatments for DO, for example botulinum toxin serotype A (BTX-A) (Onabotulinum A, Botox™, Allergan Ltd.) or neurostimulation.
Standardisation of the urodynamic assessment
Urodynamics is a skilled procedure, which requires training in setting up the UDS equipment, calibration of the machine, interpreting the pressure/flow recordings and counselling patients. One of the difficulties often encountered during UDS is the ability to identify artefacts and interpret the results.5 One of the key aspects of maintaining the accuracy of UDS is to ensure that the initial resting pressures are correct and recognised.8 Previous studies showed that even under ideal test–retest conditions, reliability can be poor for many urodynamic parameters.9,10 In clinical settings in which UDS is performed, this can be further compromised by inconsistencies in practice. The site-to-site variation in UDS procedure may have resulted from difference in equipment and training of staff.3 Quality control is a process through which procedure quality is maintained or improved, errors reduced or eliminated and is a crucial element of the good urodynamic practice (GUP) guidelines, which were developed following poor quality control observed during review of UDS traces from multicentre trials by the International Continence Society in 2002.6
Acceptability of urodynamics
Women experience significant emotional distress in relation to diagnostic evaluation.37 UDS is an intimate and invasive test13 involving the catheterisation of the bladder and rectum/vagina and some provocative manoeuvres.13 A significant number of people who undergo UDS find it embarrassing, painful or distressing.38,39 These feelings can be relieved by appropriate interpersonal skills, communication skills, maintenance of privacy and confidence in the technical ability of the health-care professional.40 Younger women and those with a history of anxiety or depression, and those receiving a diagnosis of OAB and painful bladder syndrome have been reported to have more negative experiences during UDS.41 Female patients found that UDS was more embarrassing when carried out by a male examiner, although they felt it less painful than their male counterparts. Patients with higher ‘bother’ scores may not tolerate UDS as well as a patient who has a lower bother score.38
Bladder ultrasonography
Ultrasonography has been claimed to be a potentially accurate and reliable test of DO and definitely is a less invasive method of diagnosis of DO through direct measurement of bladder wall thickness (BWT), an increase of which has been shown to be associated with DO.21,42 The bladder can be visualised by transabdominal, transperineal and transvaginal scanning. Transvaginal scanning is considered the optimal method of measuring BWT in women as the probe is closest to the bladder and captures high-quality images. Ultrasonographic measurement of BWT or detrusor wall thickness (DWT) both visualise and quantify bladder wall hypertrophy, but differ in their extent of measurement. BWT includes the detrusor, the mucosa and the adventitia of the bladder wall, while DWT includes only the detrusor. BWT values thus always exceed DWT values in the same patient, rendering them incomparable.43
In one study, female adults with normal UDS pressure patterns had a mean BWT of 3.9 mm [interquartile range (IQR) 3.4–4.5 mm].44 Another study of 166 women without urinary symptoms found a mean BWT 3.04 mm [standard deviation (SD) 0.77 mm; range 1.2–7.6 mm] and a small positive correlation between the increase in age and BWT. The small increase in BWT with age could be related to detrusor hypertrophy or secondary to increased interstitial collagen deposition.45 As the age-related increase in the thickness is small, and smaller than the likely measurement error of ultrasonography, correction with respect to age may not be required.46
The optimum bladder volume to measure BWT is still a matter of debate. In our clinical practice, we measured BWT at a bladder volume < 30 ml. BWT is known to be fairly constant when bladder volumes are measured in the range from 0 to 50 ml.44 Bladder outline is difficult to visualise at higher bladder volumes. Transabdominal measurement of BWT needs higher bladder volumes of around 250 ml, leading to more stretching of the bladder wall. BWT decreases rapidly between 50 ml and 250 ml of bladder filling (or until 50% of bladder capacity) but reaches a plateau with only minor changes thereafter.43
Evidence for the accuracy of ultrasonographic measurement of bladder wall thickness in diagnosis of detrusor overactivity
There has been conflicting evidence in the literature on the diagnostic accuracy of BWT in diagnosing DO.47,48 A systematic review identified five studies49–53 of women with OAB symptoms, three of these studies49,52,53 used transvaginal bladder ultrasonography but different UDS methods.48 In one study of transvaginal bladder ultrasonography from which accuracy data could be extracted, a BWT cut-off point of 5 mm gave a sensitivity of 84% (95% CI 76% to 89%) and specificity of 89% (95% CI 90% to 96%) for identifying DO, compared with video cystourethrography and ambulatory UDS.49 In another study, BWT varied significantly between UDS-defined lower urinary tract conditions – the mean BWT was 3.78 mm (SD 0.39 mm) for USI, 4.97 mm (SD 0.63 mm) for DO and 6.01 mm (SD 0.73 mm) for bladder outflow obstruction; p < 0.0001.54 This study reported an area under the receiver operating characteristic (ROC) curve of 0.94 (95% CI 0.89 to 0.99) for the differentiation between USI and DO or bladder outflow obstruction and 0.87 (95% CI 0.78 to 0.97) to differentiate DO and bladder outflow obstruction, suggesting thresholds of 4.1 mm and 5.6 mm, respectively, for maximal diagnostic accuracy.54 A subsequent update to the review identified seven further studies that have shown a significantly increased BWT in patients with DO than in patients without DO.27,50,55–59 However, the heterogeneity in the methods, including the standardisation of bladder ultrasonography and of UDS, and poor reporting of the proportions of DO cases identified as well as missed, precludes a formal diagnostic meta-analysis. Other methodological weaknesses of prior studies include unclear description of how bladder ultrasonography and UDS results were blinded to each other, recruitment mainly from a single centre and retrospective design.
Acceptability of bladder ultrasonography
Transvaginal bladder ultrasonography is a less invasive technique than UDS. The acceptability and psychological impact of transvaginal scanning has been extensively studied. In a study of 755 pregnant women undergoing transvaginal scanning, 272 (36%) experienced some pain or physical discomfort,60 the majority (92%) describing it as ‘mild’ or ‘discomforting’, but a small minority found the scan ‘distressing’ (5%), ‘horrible’ (3%) or ‘excruciating’ (1%). The level of psychological trauma, measured by the impact of event score (with ratings of symptoms of avoidance and intrusion) was low, with a mean of 4.3 out of a possible maximum score of 40. The majority of the women (86%) said they would definitely or probably have a repeat scan in the future.
Rationale for the study
Urinary symptoms alone can be unreliable in establishing the diagnosis of DO in women with symptoms of OAB, so clinical guidelines recommend UDS. UDS is invasive, poorly tolerated by patients and costly with an associated risk of urinary tract infections (UTIs). The mean BWT, as determined by bladder ultrasonography, appears to be higher in women with UDS defined DO and, therefore, may have a potential discriminatory role. Existing studies were small and of variable quality and further research into the role of bladder ultrasonography in diagnosis of DO in women with OAB symptoms is required.48 If shown to be accurate, reproducible and cost-effective, bladder ultrasonography would reduce the need for UDS.
In the absence of comprehensive evidence on the accuracy of UDS and its role in influencing the appropriate treatment pathway, the necessity of UDS has increasingly started to be questioned. In women with uncomplicated stress urinary incontinence (SUI), evidence suggests that UDS is not a necessary or cost-effective component in the treatment pathway.61–65 However, for women with predominant symptoms of OAB, the evidence is still inconclusive. On the one hand, studies conclude that urodynamic evaluation is essential in the management of women with symptoms of OAB,29 which is not a reliable indicator of DO in women.17 On the other hand, others conclude that an urodynamic observation of DO is not a good predictor of the outcome of a variety of treatments for OAB.66 NICE recommends the use of UDS prior to invasive treatments for OAB,36 but there has also been a call for further studies examining the role of bladder ultrasonography.36
Overview of the research
The Bladder Ultrasound study (BUS) was a prospective multicentre diagnostic accuracy study to evaluate the accuracy of BWT in diagnosing DO. The study compared BWT measurement derived from transvaginal bladder ultrasonography with a reference standard of multichannel UDS used to verify the presence or absence of DO and other UDS defined diagnoses. Consecutive women with OAB symptoms who satisfied the eligibility criteria were approached. Consenting women with OAB symptoms were characterised by their clinical history and frequency, severity and ‘bother’ of their symptoms using a bladder diary and validated questionnaire International Consultation on Incontinence modular Questionnaire Overactive Bladder (short form) (ICIQ-OAB).67 The interobserver and intraobserver reproducibility of bladder ultrasonography was assessed in substudies (see Chapter 4). Pain, embarrassment and acceptability of the two tests were assessed. An economic evaluation would compare different diagnostic strategies and treatments, using study and published data (see Chapter 7), to determine the most cost-effective diagnostic route. Women were also followed for 12 months following the investigations and the relationships between UDS diagnosis and bladder ultrasonographic measurement with treatments and symptoms were assessed.
Methodology for determination of the accuracy of bladder ultrasonography
Evaluation of the accuracy of a diagnostic test involves comparing the findings a new test with a reference standard diagnosis, which may be based on one or several pieces of test information. Accuracy focuses on estimating rates of test errors: false negatives – those who have the condition but who wrongly receive a negative test result; and false positives – those who do not have the condition but wrongly receive a positive test result. Sensitivity describes the ability of the test to correctly identify the disease (i.e. not give false-negative results) and specificity the ability to identify those without the disease (i.e. to not give false-positive results). For the evaluation of bladder ultrasonography, the findings of UDS are used for the reference standard as it is the best test for diagnosing DO. For bladder ultrasonography to be considered as a test to replace UDS, it is necessary for the rates of false negatives and false positives to be low (i.e. sensitivity and specificity to be high).
There are many possible sources of bias in accuracy studies68 and we report our study in accordance with the Standards for Reporting of Diagnostic Accuracy statement to ensure that the risk of bias can be assessed.69 There are three main domains of bias: (1) selection of the sample, (2) verification of the reference standard and (3) completeness of the data. Selection bias may arise if the sample is not suitably representative of the population. This is likely to occur with use of non-consecutive or convenience sampling. The BUS sought to approach all consecutive eligible women. A related issue is that of spectrum bias whereby the accuracy of tests varies among study samples with differences in disease severity (a measurable characteristic). We planned subgroup analysis to explore the variation in test accuracy owing to spectrum composition.
Empirical studies have shown that studies with differential verification, whereby the reference standard use is dependent on the index test result, produce more biased estimates of accuracy than studies with complete verification by the preferred reference standard.70 Some of the studies of bladder ultrasonography have mixed reference standards according to the results of the index test, which can lead to bias.44,49,52 This has occurred through using ambulatory UDS in selected subsets of patients selected according to the results of bladder ultrasonography. Although ambulatory UDS is probably a more accurate reference standard than standard UDS, it was available in only a single recruiting centre, and is costly and inconvenient, and thus we could not use it in all centres. We did aim to include a subset of patients in whom ambulatory UDS had been carried out on and use this enhanced reference standard in a sensitivity analysis, but the primary analysis is based on standard UDS assessments. We mandated that both tests were completed to ensure that we had complete data to enable the accuracy assessment to see if bladder ultrasonography can replace UDS.71
Reproducibility of a test
The accuracy of a diagnostic test relates to its ability to detect differences in measurements between individuals related to disease state (the signal) against a background of variability in measurements caused by measurement error (the noise or analytical variability). Tests may fail when there is little signal or when the magnitude of the noise is high compared with the size of the signal. Studies of reliability and reproducibility provide estimates of analytical variability and allow assessment of the ability of a test to detect real differences of varying magnitude. For imaging studies, there are two core sources of analytical variability: first, relating to the interpretation of images, with variability caused by measurement error within an observer (intraobserver) and between observers (interobserver); and second, relating to the imaging technique.
Any newer diagnostic test developed to assess bladder function accurately should ideally be reliable and reproducible and easy to interpret. Reproducibility of BWT is of particular importance given the fact that the bladder is a distensible organ and its thickness is known to inversely correlate with the amount of urine present in the bladder.46 Intraobserver and interobserver reproducibility is demonstrated by studying the difference between blinded observers/measurements when exposing the same patient to the technique independently at different points of time. Transabdominal and transperineal measurement of BWT was shown to have higher interobserver variation than transvaginal measurement in a study by Panayi et al.72 Hence we chose transvaginal measurement of BWT to evaluate diagnostic accuracy in diagnosing DO.
Assessing the acceptability of bladder ultrasonography and urodynamics
Extreme anxiety disrupts and unsettles behaviour by lowering the individual’s concentration and affecting their self-confidence and muscular control. Unsettled behaviour during intimate and invasive tests such as UDS and bladder ultrasonography may have an impact on the level of co-operation gained from the patient, the ability to complete the test and may have an adverse effect on interpretation of test results.73,74
There is no reported literature on the explicit quantification of the anxiety levels elicited by UDS and very little attention has been paid to the psychological impact of invasive diagnostic testing of lower urinary tract conditions.26 We aimed to assess state anxiety, defined as a mood state associated with preparation for possible upcoming negative events75 and consider this alongside pain during and shortly after each test.
Effect of tests on subsequent treatment pathway
Pharmacotherapy is considered first-line treatment of OAB, with or without the use of conservative interventions like bladder retraining, pelvic floor muscle training (PFMT) (with or without biofeedback), weight loss and fluid management. The motor nerve supply to the bladder is via the parasympathetic nervous system (via sacral nerves S2, S3, S4),76–78 which stimulates detrusor muscle contraction. This is mediated by acetylcholine acting on muscarinic receptors at the level of the bladder. Cholinergic blockade may abolish or reduce the intensity of detrusor muscle contraction.79 Various anticholinergic medications differ with respect to efficacy, tolerability and side effect profile. Women taking anticholinergic medications frequently experience adverse effects such as dry mouth, headache, constipation, dizziness, decreased visual acuity and tachycardia. A pharmacological classification of bladder agents used in OAB is:
Non-selective anticholinergics: tolterodine tartrate, trospium chloride, oxybutynin hydrochloride, propiverine hydrochloride, propantheline bromide.
M2–M3 selective anticholinergic: solifenacin succinate (Vesicare®, Astellas).
M3 selective antagonist: darifenacin hydrobromide (Emselex®, Merus).
Beta3 receptor agonist: mirabegron (Betmiga®, Astellas).
In patients who are refractory to conservative management of OAB (because of either a lack of efficacy or troublesome adverse effects), BTX-A has been used for over a decade with successful outcomes. The majority of patients who commence treatment with BTX-A may require long-term repeat treatments.80 There is evidence of sustained reductions in UI episodes and increase in volume/void as well as QoL in patients with neurogenic DO81 on repeat (up to five) injections with BTX-A.
Percutaneous tibial nerve stimulation (PTNS) involves stimulation of the posterior tibial nerve in the ankle using a fine-gauge needle, given weekly for 12 weeks and topped up as required. Improvement in OAB symptoms using PTNS is comparable to the effect of antimuscarinics but with a better side effect profile.82 The studies included in the published systematic review considered only short-term outcomes after initial treatment.82 In order to recommend PTNS as a practical treatment option, long-term data and health economic analysis are needed.82 The NICE guideline on UI recommends that PTNS for OAB can be offered only if there has been a multidisciplinary team review, conservative management including OAB drug treatment has not worked adequately and the woman does not want BTX-A or percutaneous sacral nerve stimulation (SNS).36
Sacral neuromodulation involves implantation of a permanent sacral nerve root stimulator, which is designed to stimulate the third sacral nerve root. It is recommended to patients with refractory OAB who have failed conservative measures (including drugs), who have not responded to BTX-A treatment and have voiding difficulties.36,83 The surgical treatment for SUI is offered if the PFMT has been unsuccessful or declined and mainly consists of a mid-urethral sling.36
The impact of a test is whether or not it ultimately improves patient outcomes, by identifying those that need treatment, or differentiating between alternative diagnoses and directing an appropriate treatment. There are widely held concerns that although a UDS DO diagnosis is accurate, it is not clear that it leads to different patient management or predicts patient outcome. There are some studies to suggest that patient-related outcomes are similar whether or not there is an urodynamic diagnosis of DO in patients with OAB, following a variety of treatment options.84–87
A comparable situation exists for stress incontinence, whereupon non-invasive assessments alone were found to be not inferior to UDS for outcomes at 1 year in a randomised controlled trial (RCT).61 A meta-analysis has concluded that pre-operative UDS does not influence the likelihood of subjective cure or post-operative complications in women without VD undergoing primary surgery for uncomplicated SUI and so should not be carried out.88 In a RCT, urodynamic status could not predict treatment outcomes between patients treated with extended-release tolterodine tartrate or placebo.84
There is a necessity, therefore, to establish the role of UDS and its impact on treatment and patient outcomes in OAB as at present its role is unclear. The BUS provided a unique opportunity to address this question and so, midway through, we proposed an extension to the study. The extension aimed to establish if treatment pathways differed following confirmation of DO based on UDS. Moreover, we sought to assess if the UDS diagnosis had an effect on patient-reported severity and improvement at 6 and 12 months after testing, and whether or not receiving the most appropriate treatment according to the UDS diagnosis improved symptoms.
Economic evaluation of the alternative diagnostic strategies
In addition to evaluating the reproducibility, accuracy and acceptability of bladder ultrasonography, it is important to assess the cost-effectiveness of testing strategies involving bladder ultrasonography, UDS and based on the primary presenting symptom in clinical history alone. The BUS would enable comprehensive primary resource utilisation for bladder ultrasonography and UDS to be collected as part of the study and the extension provided the opportunity to collect outcome data for all women who having reported bladder problems, and the treatment they received, whether or not they had a UDS diagnosis of DO. These data, together with other estimates obtained from the literature,89–92 were used to clarify whether or not the UDS test itself represents an appropriate and justifiable use of health service resources, given the doubt over its predictive ability.
Aims and objectives of the Bladder Ultrasound Study
The original primary research objective was to estimate the diagnostic accuracy of BWT, measured by transvaginal bladder ultrasonography, in the diagnosis of DO.
The original secondary research objectives were:
to conduct a decision-analytical model-based economic evaluation comparing the cost-effectiveness of various care pathways (including pathways that incorporate bladder ultrasonography)
to investigate the acceptability of UDS and bladder ultrasonography
to assess whether or not measurements of BWT made using transvaginal ultrasonography have adequate reliability and reproducibility to be likely to detect differences in BWT potentially indicative of disease.
We also aimed to investigate the value added by bladder ultrasonography to information already obtained from routinely used initial non-invasive tests (history, bladder diary, disease-specific QoL questionnaire), but this became redundant when the accuracy of bladder ultrasonography was found to be poor. Subsequently, a fifth objective was added to the BUS, namely to establish the role of UDS and its impact on treatment and patient outcomes in OAB and MUI. There were six key questions:
Does the UDS diagnosis affect treatment pathways?
What were the patient-reported outcomes in the cohort of women recruited in the BUS at 6 and 12 months after testing?
Does the diagnosis by UDS have any effect on symptoms after 6 and 12 months, that is, can UDS predict improvement in different patient groups?
Does receiving treatment concordant with the urodynamic diagnosis improve patients’ symptoms, compared with not receiving a concordant treatment?
Are presenting symptoms related to outcomes at 6 and 12 months?
Does ultrasonographic measurement of BWT have any prognostic value?
What is the cost-effectiveness of UDS in the diagnosis of DO?
