Responsiveness and minimally important difference of SF-6D and EQ-5D utility scores for the treatment of pelvic organ prolapse

Background Utility preference scores are standardized, generic, health-related quality of life (HRQOL) measures that quantify disease severity and burden and summarize morbidity on a scale from 0 (death) to 1 (optimal health). Utility scores are widely used to measure HRQOL and in cost-effectiveness research. Objective To determine the responsiveness, validity properties, and minimal important difference (MID) of utility scores, as measured by the Short Form 6D (SF-6D) and EuroQol (EQ-5D), in women undergoing surgery for pelvic organ prolapse (POP). Materials and Methods This study combined data from 4 large, U.S., multicenter surgical trials enrolling 1321 women with pelvic organ prolapse. We collected condition-specific quality of life data using the Pelvic Floor Distress Inventory (PFDI) and Pelvic Floor Impact Questionnaire (PFIQ). A subset of women completed the SF6D; women in 2 trials also completed the EQ5D. Mean utility scores were compared from baseline to 12 months after surgery. Responsiveness was assessed using effect size (ES) and standardized response mean (SRM). Validity properties were assessed by (1) comparing changes in utility scores at 12 months between surgical successes and failures as defined in each study, and (2) correlating changes in utility scores with changes in the PFDI and PFIQ. MID was estimated using both anchor-based (SF-36 general health global rating scale “somewhat better” vs “no change”) and distribution-based methods. Results The mean SF-6D score improved 0.050, from 0.705 ± 0.126 at baseline to 0.761 ± 0.131 at 12 months ( P P Conclusion The SF-6D and EQ-5D have good validity properties and are responsive, preference-based, utility and general HRQOL measures for women undergoing surgical treatment for prolapse. The MIDs for SF-6D and EQ-5D are similar and within the range found for other medical conditions.