Adequate Relief in a Treatment Trial With IBS Patients: A Prospective Assessment

Abstract

Background: Adequate relief of IBS symptoms (IBS-AR) has been used as a primary endpoint in many randomized controlled trials of IBS and is considered by the Rome III Committee to be an acceptable primary endpoint. However, controversy exists on whether baseline severity confounds the effect of this treatment patient outcome. Aims: In a randomized controlled treatment trial (1) to compare subjective report of IBS-AR to global assessment of improvement (IBS-GAI), change in IBS symptom severity scale (IBS-SSS) and IBS Quality of Life (IBS-QOL); (2) to explore whether initial IBS symptom severity influences the sensitivity of these outcome measures; (3) to determine whether psychological symptoms influence the sensitivity of these measures. Methods: 289 adult IBS patients were recruited to a treatment trial. Baseline IBS-SSS scores were used to classify IBS severity as mild (<150), moderate (150-300), or severe (>300). Questionnaires were completed at baseline and after 3 weeks of treatment with sham acupuncture or waitlist control. Results: IBS baseline severity significantly affected the proportion of patients who reported IBS-AR at 3 weeks (mild, 70%; moderate, 49.7%; severe, 38.8%) (p<0.05). However, once the patients who reported IBS-AR at baseline (28.0%) were excluded from the analysis, baseline severity no longer affected the proportion of patients reporting IBS-AR. Baseline severity did not have a significant of effect patients reporting moderate or significant improvement on the IBS-GAI (mild, 30%; moderate, 25.3%; severe, 18.8%) (p=NS). Psychological symptoms had no significant correlations with responders after adjusting for baseline severity. Conclusions: These data suggest that IBS-AR as an endpoint is confounded with initial IBS symptom severity as measured by baseline reporting of adequate relief. The confounding effects of adequate relief can be eliminated if patients who report adequate relief at screening are excluded from study participation.