Objectives:Validated tools to assess opioid-induced constipation (OIC) are needed. The aim of this study was to validate a Bowel Function Diary (BF-Diary) that includes patient-reported outcomes (PROs) associated with OIC.Methods:In a multicenter, observational study, opioid-naive or recently untreated (14 days) adults with nonmalignant, chronic pain who were prescribed oral opioid and usual care completed an electronic diary daily for 2 weeks. Test-retest reliability was assessed. Validity was evaluated for two composite end pointsnumber of spontaneous bowel movements (SBM) and complete SBMs (SCBM)and for other relevant PROs.Results:Of 238 patients (mean age 54 years, 58% women), 63% reported constipation. The intraclass correlation coefficient for numbers of SBM and SCBM, and other BF-Diary PROs was 0.71 for all items except stool consistency. Mean (s.d.) number of SBM per week was significantly less in each week for patients with vs. without constipation (5.64.3 and 7.33.6, respectively over week 1, P=0.0012; similarly, P<0.0096 over week 2). Validity of individual items in the BF-Diary was supported (P<0.05, stool consistency; P<0.0001, all others).Conclusions:BF-Diary items are generally reliable and valid assessments for OIC research. Specifically, number of SBM is a valid measure for differentiating opioid-treated patients with and without constipation.
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