Evaluation of a questionnaire in the assessment of patients with faecal incontinence and constipation

Background: A self-reported questionnaire may be a useful instrument in assessing patients with faecal incontinence and constipation. Methods: Reliability, discrimination, validity, and sensitivity were evaluated in 16 control subjects, 36 patients with faecal incontinence, and in 38 with constipation. The reliability was measured by a test-retest procedure (kappa (kappa) statistics or Spearman rank test), and validity by comparing the questionnaire and a diary. Discrimination was assessed by comparing the patient groups with the controls, and sensitivity by comparing selected answers before and after treatment. Results: Overall reliability (faecal incontinence group, mean kappa = 0.57; constipation group, mean kappa = 0.60; controls, mean kappa = 0.95) and validity were judged acceptable. In the incontinence group occurrence of faecal incontinence per se was reproducible (kappa = 0.66), as was the need to wear a pad (kappa = 0.85). Stool frequency, percentage toilet time spent straining and digitation was reproducible in patients with constipation (kappa = 0.80, r = 0.56; p < 0.001, kappa = 0.83 respectively). Several items distinguished both patient groups from healthy controls (p < 0.05 to p < 0.001). Sensitivity to surgical treatment was seen in several items in both patient groups. Conclusions: The questionnaire appears to be a valid measure of symptoms in faecal incontinence and constipation with sufficient discriminatory capacity.