Mapping the Gastrointestinal Quality of Life Index to short-form 6D utility scores

J Surg Res. 2014 Jan;186(1):135-41. doi: 10.1016/j.jss.2013.08.006. Epub 2013 Aug 28.


Purpose: The Gastrointestinal Quality of Life Index (GIQLI) is a disease-specific quality of life instrument that is commonly used in gastrointestinal disorders. However, no preference weights, which are used to calculate quality-adjusted life years for cost-effectiveness analyses, for this instrument have been assigned. Therefore, the objective of this study was to develop a mapping function to derive utility scores for the GIQLI.

Methods: Patients undergoing elective laparoscopic cholecystectomy completed the short-form 6D (SF-6D), a preference-weighted utility measure, and the GIQLI at baseline and at 1 wk and 1 mo postoperatively. The responsiveness of the SF-6D to expected postoperative changes as well as the correlation between the SF-6D and the GIQLI was investigated. Ordinary least squares regression was performed to derive a mapping function using the baseline values, which was then validated using postoperative values. Adjusted r(2), mean absolute error, and root mean square error was used to determine model performance.

Results: A total of 50 patients were included in the study (mean age 51.1 [standard deviation 16.8], 28% male). The SF-6D and GIQLI domains were responsive to expected postoperative changes, and there was high correlation between the SF-6D and four of the five GIQLI domains (excluding treatment effects). The final mapping function explained 63% of the variance in the derivation sample but had relatively high mean absolute error (0.075 and 0.067 in the 1-wk and 1-mo samples, respectively) and adjusted root mean square error (13.1% and 12.0% in the 1-wk and 1-mo samples, respectively).

Conclusions: The GIQLI can be accurately mapped to SF-6D preference weights at the group level but may be too inexact at the individual level.

Keywords: GIQLI; SF-6D; Utility mapping; laparoscopic cholecystectomy; postoperative recovery.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Cholecystectomy, Laparoscopic / psychology*
  • Female
  • Health Status*
  • Humans
  • Least-Squares Analysis
  • Male
  • Middle Aged
  • Quality of Life*
  • Quality-Adjusted Life Years