OBJECTIVES: To develop the Bowel Cleansing Impact Review (BOCLIR), a new questionnaire designed to assess patient response to bowel cleansing products, and to assess the psychometric and scaling properties of the new measure.
METHODS: Instrument content was derived via qualitative interviews conducted with patients in the UK. Face and content validity were assessed via patient cognitive-debriefing interviews. Psychometric and scaling properties were assessed via a survey. Patients completed the BOCLIR and demographic questions prior to colonoscopy. Item response theory (Rasch analysis) was employed for item reduction and unidimensionality. Internal consistency and construct validity (association of BOCLIR scores with known factors) were also assessed.
RESULTS: Qualitative interviews (n = 40/58%M) highlighted key areas of patient concern as; satisfaction with the bowel cleanser, impairments (adverse events) and activity limitations. A draft questionnaire was constructed comprising three scales addressing these areas. Cognitive-debriefing interviews (n = 19/63%M) demonstrated BOCLIR’s acceptability, relevance, clarity and ease of completion. Survey sample: n = 166/52%M, mean age 54.3/SD 15.2 years. Application of Rasch analysis removed misfitting or redundant items. Final scales fit the Rasch model as indicated by non-significant c2 p-values (p greater than 0.13 for all scales), confirming unidimensionality. Cronbach’s alpha coefficients were high indicating good internal consistency; Satisfaction 0.84, Impairments 0.77, Activities 0.94. There were significant differences in BOCLIR scores between patients based on their willingness to use the product in future and on ease of drinking the full preparation (p less than 0.01). For Impairments and Activities scales significant differences were also observed between patients dependent on how well they felt and satisfaction with the preparation (p less than 0.001).
CONCLUSIONS: The BOCLIR is a new questionnaire comprised of unidimensional scales (satisfaction, impairments and activities) with good psychometric and scaling properties. The BOCLIR will allow accurate assessment of patients' response to bowel cleansing preparations.
