Test-retest Reliability of 20-minute Pad Test

Overview

In our department, we performed a 20-minute pad test since 2005. The 20-minute pad test uses 250 mL of sterile water instilled directly into an empty bladder with a catheter rather than relying on walking for 30 minutes at the beginning of a one-hour pad test. We previously reported that 20-minute pad test has better sensitivity than the one-hour pad test in women with stress urinary incontinence (SUI). Due to the different bladder capacity in each patient, we tried to infuse strong-desire (SD) amounts of water that can more precisely reflect the full bladder capacity in each patient. We found an even better sensitivity when the 20-minute pad test was infused with SD amount of water in women with SUI compared with infusion with 250 mL of water in the bladder. As to short-term pad test, previous studies had some concerned about the reliability and reproducibility. Thus, undertaking our previous two studies, we want to evaluate the test-retest reliability of the 20-minute pad test infused with SD amount of water in bladder in women with SUI.

Between August 2007 and December 2010, a total of 89 women with SUI were recruited. Of them, 67 (75%) women who had fulfilled the standardization of terminology of lower urinary function from ICS were diagnosed as urodynamic stress incontinence (USI) after urodynamic study (UDS) and enrolled for analysis in this study. Our 20-minute modified pad test was described previously proposed first by Hahn and Fall and modified by Sand and Ostergard. Each patient's bladder was emptied with a transurethral catheter and filled to the SD amount of sterile water for test. The catheter was removed, and then the patient returned to a standing position with a pre-weighed perineal pad placed on the underwear. The patient was asked to cough 10 times, bear down 10 times, do 10 deep knee bends, jump up and down on the spot 10 times, wash her hands under cold water for 1 minute, walk up and down five stairs 10 times, walk in the hall for 10 minute, and then return for removal of the pad. The pad was then weighed and the net weight was calculated by subtracting from the original dry weight to achieve a measure of the total urine loss during the 20 minute exercise. The pad weight was measured in grams and the accuracy of the scale was 1 gram. The positive pad weight result was defined as more than 1 gram of leakage. Each woman underwent a complete UDS before pad test, including uroflowmetry, filling (with a rate of 60mL H2O/min of 35℃ distilled water) and voiding cystometry, and stress urethral pressure profile using a two-way NO.7 French flexible Foley catheter with the SD amount in the bladder. The retest twenty-minute pad test infused with SD amount water in bladder was performed within one week after first pad test. The activities that the patients underwent were the same in test and retest 20-minute pad tests. USI was diagnosed if involuntary urine leakage was noted during filling cystometry, associated with increased intra-abdominal pressure, in the absence of a detrusor contraction. Detrusor overactivity (DO) was diagnosed if involuntary detrusor contraction occurred during filling cystometry. The exclusion criteria included no obvious USI, clinically significant urinary tract infection (UTI), and chronic pelvic inflammation. The procedures and study purpose were completely explained to the participants with fully informed consent. A multichannel urodynamic equipment (Life-Tech, Houston, TX, USA) with computer analysis and Urovision (Urolab Janus System V, Houston, Tex) was used. All terminology conformed to the standards recommended by the ICS and Urodynamic Society. All procedures were performed by an experienced technician, and the data were interpreted by a single observer to avoid inter-observer variability. STATA software (Version 11.0; Stata Corp, College Station, TX, USA) was used for statistical analyses. Spearman rank-correlation coefficient and intraclass correlation coefficient were tested for correlation and reliability of the test and retest results. The Wilcoxon signed rank test was tested for the difference of the test and retest. A p value of less than 0.05 was considered statistically significant.