Development of a symptom severity index and a symptom impact index for stress incontinence in women

Stress incontinence is a common problem among women, yet there is no adequately validated instrument for measuring women's views of its severity (disease-specific health status). The only instrument for measuring the impact or bothersomeness of symptoms (disease-specific quality of life) has poor internal consistency. This paper describes the development and psychometric assessment of two new indexes, a Symptom Severity Index and a Symptom Impact Index. Following several qualitative enquiries, a questionnaire was developed and administered to 442 women undergoing stress incontinence surgery. The face and content validity of the items comprising the indexes was good. The Severity Index (0-20) showed good variability (median 14, interquartile range 6) and adequate internal consistency (alpha 0.76). The Impact Index (0-12) also had good variability (median 5, interquartile range 3.5) and internal consistency (alpha 0.80). Convergent and discriminant validity were demonstrated for both indexes. Test-retest reliability was high. While responsiveness is still to be tested, the two indexes are psychometrically strong and can be used to measure the severity and impact of stress incontinence in women.