Background and objective: Although constipation affects quality of life, questionnaires hardly exist for its evaluation. We aimed to develop and validate a questionnaire able to measure the quality of life in patients with constipation.
Patients and method: A Spanish multicenter study was performed in 2 stages: a) questionnaire development (open interview to patients with constipation, pilot questionnaire, quantitative and factorial analysis, Rasch analysis, and specific questionnaire design), and b) questionnaire validation in 136 patients. These patients were divided in 2 groups: a) reliability group (n = 55; no need to begin or change treatment; re-tested after 15 days), and b) sensibility to change group (n = 81; need to begin or change treatment; re-tested after 3 months). We collected clinical and socio-demographic data and we evaluated the quality of life through the general questionnaire EuroQoL-5D (EQ-5D) and the specific one, design in the previous stage (25 items). After that, we analysed feasibility, reliability and validity (of content, convergent and longitudinal).
Results: The trial questionnaire was obtained during the development stage and the results were 51 items that were later reduced to 25 in the validation stage. A total of 126 patients (93% women; mean age [standard deviation]: 43.4 [1] years) completed the study properly. The answer average time was 12 min. The content validity process reduced the questionnaire to 20 items (CVE-20) within 4 domains: emotional, general physical, rectal physical and social. The reliability was good in relation to the general punctuation (Cronbach alpha coefficient = 0.87), being in the different domains of 0.79, 0.73, 0.75 and 0.60, respectively. The construct validity showed a good correlation between the CVE-20 results and constipation severity. The CVE-20 score positively correlated with EQ -5D changes. The test and re-test reliability were good: interclass correlation coefficient = 0.89 (ranging from 0.80 to 0.88 in the different domains). The clinically relevant and minimal difference was 17 points (95% confidence interval, 11-23). The content validity showed a strong correlation between CVE-20 and constipation severity.
Conclusions: The CVE-20 is the first specific questionnaire in Spanish language for constipated patients; it is valid, reliable, sensitive to changes and it meets the psychometric requirements to be applied in daily practice and clinical trials.