Purpose: Traditional pre- and post-surgery quality of life assessments are inadequate for assessing change in health-related quality of life (HRQoL) after laparoscopic cholecystectomy (LC). This study examined whether a response shift, a change in the internal standards of a patient, occurs in patients who have received LC.
Methods: Self-administered gastrointestinal quality of life index (GIQLI) was used to evaluate preoperative, postoperative, and retrospective postoperative HRQoL. Response shifts, unadjusted treatment effects, adjusted treatment effects, and their effect sizes were calculated.
Results: In all GIQLI domains, a significant response shift was indicated by the significantly higher pre-test scores compared to then-test scores (P < 0.05). The effect size of the response shift ranged from 0.19 for the physical impairment domain of the GIQLI to 0.49 for the total GIQLI score. It was observed the treatment effect was greater after adjusting for the presence of response shift.
Conclusion: Patients who have received LC undergo a response shift that affects their outcome measurement at 6 months postoperative. Response shift is a potentially confounding factor and should be considered when designing clinical studies that employ self-administered HRQoL measures. This evidence of confounding effects warrants further study of response shift at longer intervals after LC, after other health care interventions, and in patients with varying preoperative health status.