Measuring outcomes of treatment for patients with episodic abdominal pains; conclusions from the EPISOD study

Objective: Measuring outcomes, that are relevant to both the patient and clinician, in patients with intermittent attacks of abdominal pain, remains challenging. The aim of this study was to examine several definitions of ‘success’ for patients undergoing treatment for suspected Sphincter of Oddi dysfunction and identify valid and reliable outcome measures for future research studies. Methods: The recently completed EPISOD trial incorporated several patient reported outcome measures to determine improvement in patients’ pain and disability over time. The trial’s primary outcome was dichotomized as ‘success/failure’ based on the days of disability due to episodic abdominal pain using the RAPID, a 90-day patient recall instrument. Additional measures included the SF-36, frequency and intensity of pain, and the Patient Global Impression of Change (PGIC), which were collected periodically during the long term follow up period. Correlations between the different instruments were calculated accounting for repeated measures within patients. Agreement using a dichotomized definition of ‘success’ was also examined. Results: There was a moderate negative correlation of the RAPID score with the specific SF-36 physical domain scores of bodily pain, physical functioning and role limitation. Negative correlations were expected since a higher RAPID score indicates greater role impairment and a higher SF-36 score indicates higher levels of physical functioning. Aggregated one month assessments of pain frequency correlated well with the results of the 90 day recall (r= 0.84). When comparing the dichotomized definitions of ‘success’, the RAPID and PGIC had a high percentage of agreement (72%) and a moderate kappa coefficient of 0.44 (0.23, 0.65). Conclusion: These results support the validity of the 90-day recall of the RAPID instrument and a dichotomized definition of success based on disability days in patients with intermittent attacks of abdominal pain. We recommend using the objective RAPID disability score and the subjective PGIC instrument in future studies. 120 British Journal of Gastroenterology 2019; 1(1): 120 124. doi: 10.31488/bjg.1000105