A severity index for epidemiological surveys of female urinary incontinence: Comparison with 48-hour pad-weighing tests

In epidemiological surveys of female urinary incontinence, it is not feasible to demonstrate urine loss objectively. The aim of this study was to develop a valid epidemiological instrument (a severity index) for assessing the severity of incontinence. The severity index is based on information about frequency (four levels) and amount of leakage (two or three levels). By multiplication, an index value (1-8 or 1-12) is reached. This index value is further categorized into a severity index of three or four levels. The index was compared with the results of 315 pad-weighing tests performed by 265 women in hospital and general practice. Data from an epidemiological survey were also re-analyzed by applying the four-level severity index. Mean pad-weighing results (grams per 24 hours, 95% confidence interval) for the three-level severity index was slight (6; 2-9), moderate (17; 13-22), and severe (56; 44-67). For the four-level severity index, the results were slight (6; 2-9), moderate (23; 15-30), severe (52; 38-65), and very severe (122; 84-159). Spearman's correlation coefficient for pad-weighing results and the three-level severity index was 0.47 (P < 0.01) and for the four-level severity index 0.54 (P< 0.01). The four-level severity index gave a more balanced distribution among the women in the clinical materials, and data from the epidemiological survey showed that the four-level severity index identifies a sub-group of older women with very severe incontinence. The four-level severity index seems to be a valid representation of incontinence severity as measured by pad-weighing tests in women presenting for clinical care. It should be considered a potentially valid measure of incontinence severity in epidemiological studies. Neurourol. Urodynam. 19:137-145, 2000.