Developing valid and reliable health utilities in irritable bowel syndrome: results from the IBS PROOF Cohort

Abstract

Objectives: A "utility" is a measure of health-related quality of life (HRQOL) that ranges between 0 (death) and 1 (perfect health). Disease-targeted utilities are mandatory to conduct cost-utility analyses. Given the economic and healthcare burden of irritable bowel syndrome (IBS), cost-utility analyses will play an important role in guiding health economic decision-making. To inform future cost-utility analyses in IBS, we measured and validated the IBS utilities.

Methods: We analyzed data from Rome III IBS patients in the Patient Reported Observed Outcomes and Function (PROOF) Cohort-a longitudinal multi-center IBS registry. At entry, the patients completed a multi-attribute utility instrument (EuroQOL), bowel symptom items, IBS severity measurements (IBS Severity Scale (IBSSS), Functional Bowel Disease Severity Index (FBDSI)), HRQOL indexes (IBS quality-of-life instrument (IBS-QOL), Center for disease control-4 (CDC-4)), and the Worker Productivity Activity Index for IBS (WPAI). We repeated assessments at 3 months.

Results: There were 257 patients (79% women; age=43+/-15 years) at baseline and 85 at 3 months. The mean utilities in patients with severe vs. non-severe IBS were 0.70 and 0.80, respectively (P<0.001). There were no differences in utilities among IBS with constipation (IBS-C), IBS with diarrhea (IBS-D), and mixed IBS (IBS-M) subgroups. EuroQOL utilities correlated with FBDSI (r=0.31; P<0.01), IBSSS (r=0.36; P<0.01), IBS-QOL (r=0.36; P<0.01), CDC-4 (r=0.44; P<0.01), WPAI presenteeism (r=0.16; P<0.01), abdominal pain (r=0.43; P<0.01), and distension (r=0.18; P=0.01). The utilities in patients reporting "considerable relief" of symptoms at 3 months vs. those without considerable relief were 0.78 and 0.73, respectively (P=0.02).

Conclusions: EuroQOL utilities are valid and reliable in IBS. The utility of severe IBS (0.7) is similar to Class III congestive heart failure and rheumatoid arthritis. These validated utilities can be employed in future IBS cost-utility analyses.

Figure 1

EQ5D (EuroQOL) instrument. Patients were instructed as follows: “By placing a checkmark in one box in each group below, please indicate which statements best describe your own health state today.”