Evaluation of the home pad test in the investigation of female urinary incontinence

Objective To evaluate the use of the home pad test in the management of patients with urinary dysfunction with reference to feasibility, normal data, reproducibility, compliance and accuracy when compared to video urodynamics. Design A prospective study to determine 1. the accuracy of weighing pads by healthcare workers compared to weighing by patients with a spring balance; 2. the effects of evaporation; 3. the pad weight increase in continent women; 4. the compliance over 194 tests in terms of acceptability and feasability; 5. the reproducibility in 112 women for the 24 h and 48 h tests, 6. the comparison with video urodynamic studies in 149 patients. Setting A London teaching hospital. Main outcome measures Coefficient of variation and mean deviation analysis were employed to determine the accuracy of measurement. Percentage changes in standardised wet pad weights over a period of 8 weeks were used to determine the rate of weight loss due to evaporation. The percentage of patients completing the test satisfactorily was documented. The increase in the weights of all the pads worn during the test period was measured in continent volunteers and incontinent patients. Video urodynamic diagnoses were used as the Gold Standard for comparison. Results Twelve perineal pads were weighed by 15 healthcare workers with a resulting coefficient of variation equal to 1.55 % (standard error = 0.09 %). The mean deviation between patient-measured pad weights and staff-measured weights was 49 % (SD = 132 %). Pads wetted with saline showed no difference in weight after 1 week and less than 5 % change in weight after 8 weeks, with the upper 95 % confidence limit of less than 10 % loss. The mean pad weight increase over 48 h in continent women was 7.13 g (SD = 4.32 g) giving a 95 % upper confidence level of less than 15 g. Compliance was reasonably high with 161 (83 %) carrying out the test perfectly. Test-retest analysis of the 24 h and 48 h tests showed a strong relationship with correlation coefficients of 0.90 and 0.94 respectively. The reproducibility was also good, with differences as a percentage of the mean between the first and second test being 6.9 % and 1.6 % for the 24 h and 48 h tests respectively. There was good concordance when the urodynamic study data was compared with pad weight data in terms of incontinence compared with no incontinence (kappa = 0.65), but a high false positive rate was detected for the pads. When eight of these patients with a false positive pad test had repeat video urodynamic studies, six were found to have detrusor instability on the second study. Conclusions The home pad test combined with frequency volume chart documentation is an easy test to perform. It is quite robust and reasonably reproducible. This test should be added to complement the routine urodynamic tests and may have a role in detecting occult detrusor instability.