Value of Urodynamics Prior to Stress Incontinence Surgery (VUSIS)

Design: multidisciplinary and multicentre randomized controlled trial

Study population/inclusion criteria : all women, not previously operated for stress incontinence, seeking help for urinary stress incontinence where conservative therapy in particular physiotherapy has failed and are opting and candidates for surgical therapy will be asked to participate in our study. Incontinence must have been demonstrated on physical examination and/or micturition diary. Patients can be included by gynaecologists or urologists who are cooperating in the study.

Intervention: consists of the non performance of urodynamics in the studygroup. The control group will undergo urodynamics as is at present the norm.

In all patients the next items will be recorded at inclusion:

1. History and clinical examination
2. 48h-Bladder(voiding and incontinence) diary,
3. 48h-Pad test
4. Validated Quality of Life questionnaires (SF 36, Euroqol 5D, UDI, IIQ)
5. Urinalysis for the detection of urinary tract infection.
6. Residual urine measured by ultrasound.

At this point an interim decision will be made for surgery. At that moment patients are informed about the study. After obtaining informed consent the patients are randomly assigned to undergo urodynamic testing or not. In the study group the decision for intervention will be based on the history and clinical examination only and will be the same as the interim decision which is surgery.

In the control group this decision will be based on history and clinical examination IN COMBINATION with the result of the urodynamic testing. It can be a decision to proceed with surgery (estimated at 2/3rd of the women) or conservative usually medication. The T0(moment of intervention) is defined as the moment of the first intervention which is by definition surgery in the study group and either surgery or conservative in the control group. After the intervention additional therapy is possible in both arms.

The follow-up period will be 24 months after T0 , in which the same parameters as pre-operative will be assessed.

These items will be assessed at:

6 weeks post intervention (PI) 3 months PI 6 months PI 12 months PI 24 months PI

Urodynamics, in the control group, will be performed according to ICS standards and consist of free flow, fillingscystometry, pressure flow study and a urethral pressure profilometry in rest and during stress. The outcomes will be matched to urodynamic findings to indicate the possible useful parts of the urodynamic findings.

Post operative urodynamics is NOT part of the study.

The primary outcome of this study is the improvement of Urogenital Distress Inventory (UDI) at 24 months after baseline and the power calculation is performed using the non-inferiority assumption. The mean improvement in UDI in both groups is expected to be 35 with standard deviation 10.(22) A difference in mean improvement of 8 or less is considered non-inferior. As this condition is allowed for one third of the total group (those women in the non-UDI group, who would not have been operatively treated), this results in a difference in mean improvement of 2.7 or less between the UDI and non-UDI group. Then effectively 130 women in each group are needed to reach a power of 70% using one-sided testing at 0.05. Considering an expected percentage lost to follow up of ca. 10%, in total 290 women (145 in each group) will be included in this study.

Multivariate analysis of covariance with group, centre and the baseline covariate as independent variables will be used to estimate differences in improvement of the UDI after 24 months between the groups with 95% confidence intervals. As the UDI is skewed, data will be logtransformed prior to analysis. Other variables (ie Incontinence Impact Questionnaire) will be analysed similar.

Economic evaluation:

For each patient, utilisation of health care services will be recorded prospectively, using Case Record Forms, including urodynamic testing, surgery for SUI, re-operations, medical treatment for detrusor instability, care for urinary incontinence, and care for urinary retention. By multiplying these volumes of care with unit cost prices, direct medical costs incurred by SUI during the follow up period will be calculated for each patient. For unit cost prices, national guidelines will be used (CVZ, 2004). For costs of care for urinary incontinence and urinary retention, data from the literature will be used, converted to 2006 prices. We incorporated the health related quality of life questionnaire euroqol 5D in our study to be able to calculate QALYs (quality-adjusted life-years), which is a measure of health outcomes. A QALY is the change in quality of life induced by the treatment multiplied by the duration of the treatment effect and it provides the number of QALYs gained. QALYs can then be related to medical costs to arrive at a final common denominator of cost/QALY. This parameter can be used to compare the cost-effectiveness of the treatment.