General obstetrics and gynecology: GynecologyA prospective multicenter randomized trial of tension-free vaginal tape and colposuspension for primary urodynamic stress incontinence: Two-year follow-up☆
Section snippets
Material and methods
Women with urodynamic stress incontinence unresponsive to pelvic floor muscle exercise, who had completed their family, were invited to participate. Exclusions were vaginal prolapse requiring treatment, previous surgery for incontinence or prolapse, neurologic disease, known bleeding diathesis or current anticoagulant therapy, allergy to local anesthetic, detrusor overactivity, and voiding difficulty (defined at cystometry as maximum flow less than 15 mL per second or voiding pressure greater
Outcome measures
The primary outcome measure at 2 years was cure of stress incontinence that was based on a negative 1-hour pad test (less than 1 g change in weight). Secondary outcome measures included subjective cure and the development of voiding problems, urgency, and vaginal prolapse. These were measured with the BFLUTS questionnaire, by interview with patients, and by clinical examination.
Statistical analysis
On the assumption of 90% cure after colposuspension,3 it was calculated that 197 to 262 patients would be required in each arm to detect a 10% difference in cure rate between procedures with 80% to 90% power. Our pragmatic recruitment target, based on collaborating center workloads, was 436 patients.
Data were entered into an Access (Microsoft, Redmond, Wash) database from case report forms using double data entry. Comparison of data entries was performed and discrepancies reviewed by an
Ethics
The Multicentre Research Ethics Committee as well as local ethics committees of each of the collaborating centers granted ethical approval for the trial. The trial was carried out in accordance with “Recommendations guiding research into human subjects” (Declaration of Helsinki 1975), “Good clinical practice for trials on medical products in the European Community” (WHO and ICH Tripartite Good Clinical Practice guidelines 1997), and “Clinical investigation of medical devices for human subjects”
Results
Three hundred forty-four women were randomly selected; their progress through the trial is shown in the Figure.
There were no differences in the baseline characteristics between the two groups.1 Twenty-eight patients withdrew from the trial after randomization but before surgery; 23 withdrew having been randomly assigned to colposuspension and 5 after being randomly assigned to TVT. This difference was significant (P = .0005, Fisher exact test). The baseline characteristics of patients withdrawing
Primary outcome measure
A negative 1-hour pad test was recorded in 111 (81%) patients in the TVT group and 86 (80%) in the colposuspension group at 2 years. The change in pad weight decreased significantly in both groups, from a median of 18 g (interquartile range 6-37) to 0 (interquartile range 0-0) in the TVT group and a median of 16 g (interquartile range 6-38) to 0 (interquartile range 0-0) in the colposuspension group (P = .51, Wilcoxon rank sum test [95% CIs for difference –3 to 6]). The impact of varying
Secondary outcome measures
Results from the BFLUTS questionnaire are shown in Table II. Significant changes were seen in the majority of urinary symptoms throughout the follow-up period in both treatment groups. Although differences were seen in the incidence of several symptoms, there were no significant differences in the proportion of patients reporting symptoms to be bothersome for these items with the exception of daytime frequency. Only 44 (25%) women in the TVT arm and 34 (20%) in the colposuspension arm reported
Comment
Although this is one of the largest trials of surgery for stress incontinence, the statistical power is limited by the failure to recruit up to our calculated sample size because of limitations of resources and time available. This calculation was based on 90% cure for colposuspension with the aim of detecting a 10% difference between the procedures. The power of the study is dependent on the cure rate and, as has been shown by testing assumptions in relation to dropouts, this may lie between
Acknowledgements
We thank the patients and technical, secretarial, nursing, and medical staffs of the participating hospitals. We thank Professor John Matthews for statistical advice. We also thank James Browning (trial sponsor to June 2000), Marjory Willins (trial manager), Jane Gibson (trial administration), Ailie Smith (quality assurance) and the monitoring staff of Ethicon Ltd. The investigators had complete freedom to analyze the data and report the results as they saw fit.
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Information on other investigators is given in the Appendix.
Funding for the trial was provided by Ethicon Ltd. K. W. was supported by a grant from Ethicon Ltd, who also provided materials and additional support to collaborating centers. P. H. and K. W. have been reimbursed by Ethicon Ltd for conferences expenses where this, and related work has been presented; neither have any financial interest in this or any other company.