Objectives: To develop a universally applicable test instrument to measure the total direct costs of urinary incontinence, including personal costs and treatment costs, i.e. the Dowell-Bryant Incontinence Cost Index (DBICI), and to study the construct validity and test-retest reliability of the instrument.
Patients and methods: In a prospective observational study, 100 consecutive community-dwelling ambulatory women who presented with stress, urge or mixed incontinence were asked to complete the DBICI questionnaire on two occasions, 7 days apart, before any treatment. The construct validity of the DBICI was ascertained by correlation with other standard measures of urinary incontinence severity; (i) a visual analogue scale (VAS) to assess the impact of leakage upon lifestyle; (ii) frequency-volume charts (voids/24 h, leaks/week); (iii) urine loss during a standard 1 h pad test; and (iv) two disease-specific quality of life questionnaires. The test-retest reliability was measured by comparing the two test results and the construct validity of the individual subsets (personal and treatment) of the DBICI similarly assessed.
Results: Ninety-seven women completed the baseline assessment and 84 completed the re-test. The median (interquartile range) total direct incontinence cost (in Au$) was 12. 89 (5.26-22.67) per week, which comprised the median personal costs of 5.61 (1.68-10.36) and the median treatment costs of 4.96 (1.22-13. 37). The total direct incontinence cost was significantly correlated with the severity of urinary leakage on a 1 h pad test (Kendall's rank correlation, P=0.01), with the VAS impact score (P<0.001) and with the number of leaks/week (P=0.005). The correlation between the personal cost subset and other quantitative measures was also highly significant. Test-retest analysis of the personal costs subset revealed that this subset was robust and satisfied the statistical criteria of repeatability.
Conclusions: The DBICI gives a detailed measure of the direct economic costs of urinary incontinence in ambulatory home-dwelling women, with the construct validity confirmed by the significant correlation with other quantitative measures of incontinence. By substituting local prices into the test format, the index should be useful in other countries. In the current climate of economic rationalization, such an index should be a part of future urinary incontinence research.