Further validation of the psychometric properties of the Bowel Function Index for evaluating opioid-induced constipation (OIC).

OBJECTIVE: The BFI † (Bowel Function Index) is a 3-item questionnaire for assessing opioid-induced constipation (OIC). The aim of this study was to contribute to the validation of the psychometric properties of the BFI by confirming a constipation threshold, and through correlation with other validated tools: KESS (Knowles Eccersley Scott Symptom) score and generic (12-Item Short Form Health Survey, SF-12) and specific (Patient Assessment of Constipation-Quality of Life, PAC-QoL *) quality-of-life scores.

METHODS: A survey on opioid-requiring cancer-patients was carried out in France. A questionnaire was filled out for all patients that recorded their demographic characteristics, an assessment of their constipation using BFI and KESS scores, and included a self-assessment of quality-of-life using PAC-QoL and SF-12. Correlation of BFI with KESS, PAC-QoL, and SF-12 was investigated.

RESULTS: Five hundred and twenty patients participated in the entire data collection with no loss. BFI was shown to be statistically correlated (r = 0.571; p < 0.0001) with the KESS score and matches up with PAC-QoL and to a lesser extent with the SF-12 generic quality-of-life questionnaire. A BFI threshold of 27-29 to discriminate constipated from non-constipated patients was confirmed.

KEY LIMITATIONS: This cross-sectional study in a selected population of cancer pain patients has validated the psychometric properties of the BFI. Further confirmation of the validity of the BFI could be sought through the use of longitudinal studies, and larger populations, such as non-cancer pain patients treated with opioids.

CONCLUSION: This study contributes to the validation of the psychometric properties of the BFI. It confirms the BFI as an easy-to-use tool to assess constipation and its impact on quality-of-life in chronic pain patients.