The minimally important difference of the Gastrointestinal Quality of Life Index for symptomatic gallstone surgery

The Gastrointestinal Quality of Life Index (GQLI) is used to measure domains of health and symptoms among people with gastrointestinal disorders. The objective of this study is to calculate the smallest change in the GQLI that is perceived by patients as meaningful among a sample of English-speaking adult patients undergoing elective laparoscopic cholecystectomy for treatment of symptomatic gallbladder disease.

The study is based on retrospective analyses of a sample of participants completing the GQLI and the EQ-5D(3L) preoperatively and six months postoperatively in Vancouver, Canada. Patients are excluded if they are less than 19 years of age, cannot communicate in English, or reside in a long-term care facility. The MID is calculated for the GQLI's domains using distribution and anchor-based methods.

Among eligible patients, the participation rate was 51%. The estimated MID for the overall GQLI value ranged between 4.32 and 11.44. There were no statistically significant differences in the GQLI's MID values between sexes or age subgroups. There were statistically significant differences in the GQLI's MID values by baseline health status.

This study should provide some comfort that the MID values used in discussing change in health and symptoms with elective cholecystectomy patients are robust to sex. Although the sample size may have been inadequate for age-based analyses, the study found large differences in MID values between age subgroups. Statistically significant differences in MID values based on preoperative health supports reporting MID values separately by baseline value. Further research should explore whether age-based differences in MID values exist using larger samples.