Response shift in quality-of-life assessment in patients undergoing curative surgery with permanent colostomy: a preliminary study.

The purpose of this preliminary study (N 13) was to investigate the impact of response shift in quality of life for cancer patients undergoing surgical resection with resultant permanent colostomy. Response shift was measured using a "then-test" approach. Quality of life was measured using the 36-Item Short Form Health Survey version 2 (Japanese version). Baseline data (pretest scores) were collected before surgery when subjects completed the 36-Item Short Form Health Survey. Two months after the surgery, subjects were asked to respond again to the 36-Item Short Form Health Survey to assess their postsurgery quality-of-life (posttest score) level and their presurgery quality-of-life level (then-test score). Norm-based scoring for pretest, posttest, and then-test scores for each of the 36-Item Short Form Health Survey domains was calculated. Response shift was assessed by the difference between pretest and then-test scores and effect size. Findings revealed that a moderate but significant response shift was observed in the bodily pain domain. A small response shift was observed in the role physical and vitality domains. The then-test score was higher than the pretest score. The same trend was observed in all other domains except general health. The results indicate that the unit of comparison in the subjects was changed by surgery. Knowledge of these phenomena would allow a better understanding of quality of life of these subjects.