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Purpose: To investigate the presence and impact of response shift (RS) in outcomes assessment among patients undergoing total knee replacement (TKR) and explore factors associated with RS.
Methods: Consenting TKR patients without cognitive problems seen at a tertiary referral centre were interviewed in this IRB approved study to determine their Health-related Quality of Life (HRQoL) using the SF-6D at 0-months (just before surgery: pre-test1), and 6 months (pre-test2), and 18 months after surgery (post-test). RS was studied using a “then-test” approach by contacting participants 18 months after surgery and asking them to evaluate their HRQoL at 0-months (then-test1), 6-months (then-test2) and 18-months to obviate changes in internal standards. RS was calculated as the score difference between pre-test and then-test scores for a given time point. Descriptive analysis was used to characterise demographics (age, gender, education level, work status, dwelling type), medical information (presence of acute or chronic illness, past knee surgery, number of knees operated) and general satisfaction with knee surgery (on a 0-10 Likert scale). Wilcoxon Signed Rank tests were used for comparisons of RS at 0-months and 6-months. Relationships between RS and external variables were investigated by univariate analyses using Mann-Whitney, Kruskal-Wallis tests or Spearman’s correlation. Multiple liner regression (MLR) models were used to explore demographic and medical factors potentially impacting RS. Unless specified, median (interquartile range) was reported and significance level was set at 0.01.
Results: Data were analyzed from 74 subjects [63% response rate, mean (SD) age 68.9 (7.9) years, 81% female, 92% with less than 12 years of education, 14% working, 72% with acute and 68% with chronic illness, 10% with past knee surgery history, mean (SD) surgery satisfaction of 8.0 (1.3)]. SF-6D scores for then-tests at 0-months [0.48 (0.42, 0.49)] and 6-months 0.72 (0.66, 0.79) were significantly different from respective pre-test scores [0.61 (0.58, 0.68) at 0-months, 0.69 (0.63, 0.72) at 6-months, both p<0.01]. Thus RS was present at both 0-months and 6-months. Interestingly, RS at 0-months [just prior to TKR, 0.13 (0.08, 0.20)] was significantly larger than that at 6-months [i.e. post TKR, -0.03 (-0.14, 0.00)]. RS at 0-months was not affected by assessed demographic or medical variables. RS at 6-months was greater in subjects with more years of education (p<0.01, 16% of variance in MLR).
Conclusions: RS was present and impacted HRQoL assessment among patients undergoing TKR both just prior to and 6 months after surgery. This suggests that HRQoL evaluations may need to be performed bearing in mind potential changes in patients’ internal standards which lead to RS.
Methods: Consenting TKR patients without cognitive problems seen at a tertiary referral centre were interviewed in this IRB approved study to determine their Health-related Quality of Life (HRQoL) using the SF-6D at 0-months (just before surgery: pre-test1), and 6 months (pre-test2), and 18 months after surgery (post-test). RS was studied using a “then-test” approach by contacting participants 18 months after surgery and asking them to evaluate their HRQoL at 0-months (then-test1), 6-months (then-test2) and 18-months to obviate changes in internal standards. RS was calculated as the score difference between pre-test and then-test scores for a given time point. Descriptive analysis was used to characterise demographics (age, gender, education level, work status, dwelling type), medical information (presence of acute or chronic illness, past knee surgery, number of knees operated) and general satisfaction with knee surgery (on a 0-10 Likert scale). Wilcoxon Signed Rank tests were used for comparisons of RS at 0-months and 6-months. Relationships between RS and external variables were investigated by univariate analyses using Mann-Whitney, Kruskal-Wallis tests or Spearman’s correlation. Multiple liner regression (MLR) models were used to explore demographic and medical factors potentially impacting RS. Unless specified, median (interquartile range) was reported and significance level was set at 0.01.
Results: Data were analyzed from 74 subjects [63% response rate, mean (SD) age 68.9 (7.9) years, 81% female, 92% with less than 12 years of education, 14% working, 72% with acute and 68% with chronic illness, 10% with past knee surgery history, mean (SD) surgery satisfaction of 8.0 (1.3)]. SF-6D scores for then-tests at 0-months [0.48 (0.42, 0.49)] and 6-months 0.72 (0.66, 0.79) were significantly different from respective pre-test scores [0.61 (0.58, 0.68) at 0-months, 0.69 (0.63, 0.72) at 6-months, both p<0.01]. Thus RS was present at both 0-months and 6-months. Interestingly, RS at 0-months [just prior to TKR, 0.13 (0.08, 0.20)] was significantly larger than that at 6-months [i.e. post TKR, -0.03 (-0.14, 0.00)]. RS at 0-months was not affected by assessed demographic or medical variables. RS at 6-months was greater in subjects with more years of education (p<0.01, 16% of variance in MLR).
Conclusions: RS was present and impacted HRQoL assessment among patients undergoing TKR both just prior to and 6 months after surgery. This suggests that HRQoL evaluations may need to be performed bearing in mind potential changes in patients’ internal standards which lead to RS.
X. Zhang, None; S. Li, None; N. Lo, None; K. Yang, None; S. Yeo, None; J. Thumboo, None.
See more of: Epidemiology and Health Services Research III
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