Solifenacin in the treatment of overactive bladder syndrome in Italian patients: pharmacoeconomic evaluation

Review of Economic Value Drivers of the Treatment of Overactive Bladder

Overactive bladder (OAB) is a symptom-driven condition with economic burden estimated to be on the order of several hundred dollars or euros per patient in some North American and European countries. This work reviews recently published economic models to evaluate how health states are defined, what cost components are considered, and what utility values are used to estimate the cost effectiveness of OAB pharmacotherapies, botulinum toxin, or sacral neuromodulation. It was found that no clear standard exists for determining OAB health states, although most were defined by some measure of incontinence frequency. Costs of physician visits and incontinence pads were included in nearly all models; however, OAB-associated depression and nursing home costs were rarely included, despite being large cost drivers of global economic burden studies. Utility values used in the models ranged from 0.544 to 0.933, highlighting the uncertainty associated with how OAB patients value health-related quality of life. More research is warranted so that health states providing delineations among OAB symptom severity and quality of life are clinically and economically meaningful as well as meaningful to affected patients.

Bladder ultrasonography for diagnosing detrusor overactivity: test accuracy study and economic evaluation

BACKGROUND

Urodynamics (UDS) has been considered the gold standard test for detrusor overactivity (DO) in women with an overactive bladder (OAB). Bladder ultrasonography to measure bladder wall thickness (BWT) is less invasive and has been proposed as an alternative test.

OBJECTIVES

To estimate the reliability, reproducibility, accuracy and acceptability of BWT in women with OAB, measured by ultrasonography, in the diagnosis of DO; to explore the role of UDS and its impact on treatment outcomes; and to conduct an economic evaluation of alternative care pathways.

DESIGN

A cross-sectional test accuracy study.

SETTING

22 UK hospitals.

PARTICIPANTS

687 women with OAB.

METHODS

BWT was measured using transvaginal ultrasonography, and DO was assessed using UDS, which was performed blind to ultrasonographic findings. Intraobserver and interobserver reproducibility were assessed by repeated measurements from scans in 37 and 57 women, respectively, and by repeated scans in 27 women. Sensitivity and specificity were computed at pre-specified thresholds. The smallest real differences detectable of BWT were estimated using one-way analysis of variance. The pain and acceptability of both tests were evaluated by a questionnaire. Patient symptoms were measured before testing and after 6 and 12 months using the International Consultation on Incontinence modular Questionnaire Overactive Bladder (short form) (ICIQ-OAB) questionnaire and a global impression of improvement elicited at 12 months. Interventions and patient outcomes were analysed according to urodynamic diagnoses and BWT measurements. A decision-analytic model compared the cost-effectiveness of care strategies using UDS, ultrasonography or clinical history, estimating the cost per woman successfully treated and the cost per quality-adjusted life-year (QALY).

RESULTS

BWT showed very low sensitivity and specificity at all pre-specified cut-off points, and there was no evidence of discrimination at any threshold (p = 0.25). Extensive sensitivity and subgroup analyses did not alter the interpretation of these findings. The smallest detectable difference in BWT was estimated to be 2 mm. Pain levels following both tests appeared relatively low. The proportion of women who found the test 'totally acceptable' was significantly higher with ultrasonography than UDS (81% vs. 56%; p < 0.001). Overall, subsequent treatment was highly associated with urodynamic diagnosis (p < 0.0001). There was no evidence that BWT had any relationship with the global impression of improvement responses at 20 months (p = 0.4). Bladder ultrasonography was more costly and less effective than the other strategies. The incremental cost-effectiveness ratio (ICER) of basing treatment on the primary clinical presentation compared with UDS was £491,500 per woman successfully treated and £60,200 per QALY. Performing a UDS in those women with a clinical history of mixed urinary incontinence had an ICER of £19,500 per woman successfully treated and £12,700 per QALY compared with the provision of urodynamic to all women. For DO cases detected, UDS was the most cost-effective strategy.

CONCLUSION

There was no evidence that BWT had any relationship with DO, regardless of the cut-off point, nor any relationship to symptoms as measured by the ICIQ-OAB. Bladder ultrasonography has no diagnostic or prognostic value as a test in this condition. Furthermore, despite its greater acceptability, BWT measurement was not sufficiently reliable or reproducible.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN46820623.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 7. See the NIHR Journals Library website for further project information.

Cost-effectiveness analysis of solifenacin versus oxybutynin immediate-release in the treatment of patients with overactive bladder in the United Kingdom

OBJECTIVE

To carry out a cost-utility analysis comparing initial treatment with solifenacin 5 mg/day vs oxybutynin immediate-release (IR) 15 mg/day for the treatment of patients with overactive bladder (OAB) from the perspective of the U.K. National Health Service (NHS).

METHODS

A Markov model with six health states was developed to follow a cohort of OAB patients treated with either solifenacin or oxybutynin during a 1-year period. Costs and utilities were accumulated as patients transited through the health states in the model and a drop-out state. Some of the solifenacin patients were titrated from 5 mg to 10 mg/day at 8 weeks. A proportion of drop-out patients were assumed to continue treatment with tolterodine ER. Utility values were obtained from a Swedish study and pad use was based on a multinational clinical trial. Adherence rates for individual treatments were derived from a U.K. database study. For pad use and utility values, the drop-out state was split between those patients who were no longer receiving treatment and those on second-line therapy. Patients on second-line therapy who drop-out were referred for a specialist visit. Results were expressed in terms of incremental cost-utility ratios.

RESULTS

Total annual costs for solifenacin and oxybutynin were £504.30 and £364.19, respectively. First-line drug use represents 49% and 4% of costs and pad use represent 23% and 40% of costs for solifenacin and oxybutynin, respectively. Differences between cumulative utilities were small but were greater for solifenacin (0.7020 vs. 0.6907). The baseline incremental cost-effectiveness ratio was £12,309/QALY.

CONCLUSION

Under the baseline assumptions, solifenacin would appear to be cost-effective with an incremental cost-utility of less than £20,000/QALY. However, small differences in utility between the alternatives and the large number of drop-outs means that the results are sensitive to small adjustments in the values of utilities assigned to the drop-out state.