BERKELEY, CA (UroToday.com) - The objective of our study was to prospectively compare, in terms of efficacy and safety, the tension-free vaginal tape (TVT) and the transobturator vaginal tape inside-out (TVT-O) procedure for stress urinary incontinence (SUI).
A cough stress test was applied to the objective outcomes, while the urinary incontinence specific quality of life (IQoL) questionnaire was applied to the subjective outcomes. A test for non-inferiority was carried out for detecting the success rate between the 2 groups. Results: The objective success rates were 95.4% (62/65) in the TVT group and 96.4% (108/112) in the TVT-O group. No significant difference was found between these 2 groups in the success rate by the non-inferiority test (P ＜ 0.0005), with significant improvement in quality of life (QoL) and no significant difference in patient satisfaction rates in the 2 groups (P > 0.05).
In the study, the TVT-O procedure could be identical to the TVT approach in success rate by the non-inferiority test.
Several controlled, clinical studies comparing TVT-O and TVT procedures in the treatment of female stress urinary incontinence have been reported since the first report of TVT-O by Deleval in 2002. The traditional hypothesis test (t test) was used in these studies, most of which drew the conclusion that TVT-O was not inferior to TVT in efficacy and safety. However, it was not rigorous enough for these studies to draw such a conclusion.
Firstly, the suboptimal assessment of TVT-O surgery using the traditional hypothesis test may fail to determine if the efficacy of TVT-O is identical to the TVT approach due to limited sample size, error deviation, and slight differences in clinical parameters of the 2 surgical procedures. Secondly, the formula for sample-size calculation was not stated clearly in the current controlled studies. As the difference of surgical cure rate between TVT-O and TVT was very slight, according to current reports, more than 1000 cases were required if the test was employed, as calculated by the relevant formula. The sample size in the current studies was no more than 200 to 300 cases, which was obviously insufficient, and therefore reduced the reliability of these findings. In addition, the huge sample size was not an economical choice for conducting clinical studies.
Instead of using the traditional hypothesis test (statistically significant at P (0.05), the non-inferiority/equivalence test is able to access the efficacy of the 2 procedures via relatively small sample size, based on clinical values of the variable and α value of statistics.
Therefore, we carried out a test for non-inferiority for detecting the success rate between the TVT-O and TVT.
In this study, α was defined as 0.05 unilaterally, β as 0.2, and power of test as 80% (1－β). The surgical, objective success rate of TVT was 95.5%, according to the relevant literatur; i.e., P = 95.5%. Assuming the study group (TVT-O) and the control group (TVT) were equal to the overall cure rate, the physician-recognized value of non-inferiority boundary (δ) was 12%. The proportion of the study group and control group was defined as 2:1; i.e. k = 2. The corresponding value of u0.05 and u0.20 was 1.64 and 0.84. The data was substituted into the formula n ＝ 2P（1－P)[（ｕα＋ｕβ）/ δ]2 for sample size calculation, resulting in n = 41, n1 = 62, and n2 = 31. Considering a dropout rate of 20%, at least 74 cases were required in the TVT-O group and 37 cases in the TVT group.
We enrolled 112 cases in the TVT-O group and 65 cases in the TVT group in this study. We found no significant difference between these 2 groups in the success rate by non-inferiority test (P ＜ 0.0005), with significant improvement in quality of life (QoL) and no significant difference in patient satisfaction rates in the 2 groups.
Xiang Yang,1 Min Jiang,2 Xiaowen Tong,1 Xinliang Chen,3 Huaifang Li,1 Jin Qiu,4 and Lingyun Shao5 as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
1Department of Obstetrics and Gynecology, Tongji Hospital of Tongji University, 389 Xincun Road, Shanghai, China
2Shanghai Center for Clinical Laboratory, 528 Hongshan Road, Shanghai, China
3International Peace Maternity and Child Health Hospital, Jiaotong University, 910 Hengshan Road, Shanghai, China
410th People Hospital of Tongji University, 301 Yanchang Road, Shanghai, China
5Shanghai East Hospital, 150 Jimo Rd, Shanghai, China
Xinliang Chen, MD., International Peace Maternity and Child Health Hospital, Jiaotong University, 910 Hengshan Road, Shanghai, China