The quantification of urinary incontinence (UI) is widely used in clinical practice to guide prognosis and treatment, avoiding inappropriate and unnecessary interventions. A Cochrane systematic review reported that complex screening methods such as urodynamics are applied, the clinical decision changes, but it is not clear whether it contributes to enhancing clinical outcomes.(1) So, less complex objective and subjective assessment methods are employed to guide prognosis and treatment. Pad test was introduced in the 1980s, and since then different protocols have been published. The International Continence Society recommends using the 24- or 1-h pad test because of the reproductivity and reliability, but a 20-min pad test protocol has been used and compared to the 1-h pad test showed better sensitivity(2) and reproducibility(3) for stress urinary incontinence (SUI). However, reliability was not measured. The correlation between the subjective UI complaint and pad test weight is strong and positive between the total score and 1-h pad test, but the magnitude of the correlation varies with the pad test methodology. The aim of this study was to assess the correlation of the 20-min pad test with the subjective urine leakage amount reported by women with SUI or mixed urinary incontinence (MUI).

This was a cross-sectional study approved by the Institutional Ethical Committee (Protocol Number CAAE: 22869119.0.0000.5505). All subjects met the following inclusion criteria: Women with SUI or MUI (SUI as the main complaint) > 18 years old who attended regular physical therapy were included in the study. A urogynecologist performed the first research step, collecting participant’s basic information. Then, to assess the subjective urine leakage amount, the standard question on volume from the incontinence severity index (ISI) was used. The participants answered positively to the questions: “Do you leak urine accidentally?” and “How much urine do you leak each time?” The response options were drops, small splashes, or more. The next step consisted of the objective measurement of UI by 20-min pad test. The bladder was emptied by a transurethral catheter and refilled with 250 ml injected saline solution. The participants wore a pre-weighed pad and then were asked to cough ten times, bear down ten times, jump up and down in place ten times, wash their hands under cold water for 1 min, walk up and down five stairs ten times, and walk in the hall for 10 min. Ten deep knee bends were not performed because the participants had difficulty performing the movement. After exercise, the pad was weighed, and the final value was subtracted from the original dry weight to estimate the total urine loss during the 20-min exercise. The positive test was defined as > 1 g.

We reviewed and screened 83 charts of consecutive incontinent participants who attended the clinic. From these, 11 were not included because of incomplete information. Pad tests and questionnaires of 72 participants were extracted and analysed. Considering the general sample, the average age was 56 (53.7–58.9) years old, and the BMI was 29 (27.8–30.4) kg/m2. The number of pregnancies was 3 (0–16) on average, and the prevalence of vaginal delivery was 56 (77.8%). Concerning urinary complaints, 56 (77.8%) reported MUI and 16 (22.2%) SUI. Also, most participants (50.7%) reported leaking small splashes, 35.2% reported drops, and 14.1% reported larger quantities. The duration of symptoms was 48 (68.2–115.4) months; the average pad weight was 12 (15.1–26.1) g. There were no differences related to the duration of symptoms between different UI volumes. Pad weight increased according to the subjective volume reported. The pad weight was heavier for small splashes (P = 0.006) and the volume greater (P = 0.001) than for drop leakage. Spearman’s coefficient between pad weight and subjective volume of urine leakage was rs = 0.558 (P ≤ 0.0001), demonstrating a moderate to strong positive correlation (Fig. 1).

To the best of our knowledge, this is the first study to demonstrate the correlation between the 20-min pad test and subjective UI volume report. According to our results, there was a moderate correlation between the objective and subjective methods. The advantages of short pad tests are feasibility of performing the test at the office, the quick response, and, compared to longer tests, avoidance of measurement confounders such as evaporation, vaginal secretion, and mistakes made by the participants. The disadvantage is that they do not express real-life circumstances and can underestimate UI severity. Nevertheless, analyzing the results from the 20-min pad test, for participants who reported drop leakage, the range of pad weights was smaller, but as the volume reported increased, the weight range was more heterogeneous, showing that the test was not sufficient to reproduce the individual UI mechanisms. So, this should be considered when choose the pad-test duration.

There was a moderate correlation between the UI volume reported and the 20-min pad test when the symptom of SUI was the main complaint.

Clement KD, Lapitan MCM, Omar MI, Glazener CM. Urodynamic studies for management of urinary incontinence in children and adults. Cochrane Database Syst Rev [Internet]. 2013 Oct 29; Available from: http://doi.wiley.com/10.1002/14651858.CD003195.pub3
Wu WY, Sheu BC, Lin HH. Comparison of 20-minute pad test versus 1-hour pad test in women with stress urinary incontinence. Urology. 2006;68(4):764–8.
Hahn I, Fall M. Objective quantification of stress urinary incontinence: A short, reproducible, provocative pad-test. Neurourol Urodyn. 1991;10(5):475–81.