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 points--number 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 (5.6 ± 4.3 and 7.3 ± 3.6, 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.