A comparison between the EQ-5D and the SF-6D in patients with chronic obstructive pulmonary disease (COPD).
BACKGROUND
The appropriate use of generic preference-based measures determines the accuracy of disease assessment and further decision on healthcare policy using quality adjusted life years. The discriminative capacity of different instruments would differ across disease groups. Our study was to examine the difference in utility scores for COPD patients measured by EQ-5D and SF-6D and to assist the choice of a proper instrument in this disease group.


METHODS
Differences of mean utility scores of EQ-5D and SF-6D in groups defined by socio-demographic characteristics, comorbidities, health service utilisation and severity of illness were tested using Mann-Whitney test, t-test, Kruskal-Wallis test, Pearson's correlation coefficient and ANOVA, as appropriate. The discriminative properties of the two instruments were compared against indicators of quality of life using receiver operating characteristic curves. The statistical significance of the area under the curves (AUC) was tested by ANOVA and F-statistics used to compare the efficiency with which each instrument discriminated between disease severity groups.


RESULTS
Mean utility scores of EQ-5D and SF-6D were 0.644 and 0.629 respectively in the 154 subjects included in the analysis. EQ-5D scores were significantly higher than SF-6D in groups less severe and these differences corresponded to a minimally important difference of greater than 0.03 (p<0.001). EQ-5D and SF-6D scores were strongly correlated across the whole sample (r = 0.677, p<0.001) and in pre-defined groups (r>0.5 and p<0.05 for all correlation coefficients). AUCs were above 0.5 against the indicators of health-related quality of life for both instruments. F-ratios suggested SF-6D was more efficient in discriminating cases of different disease severity than EQ-5D.


CONCLUSIONS
Both EQ-5D and SF-6D appeared to be valid preference-based measures in Chinese COPD patients. SF-6D was more efficient in detecting differences among subgroups with differing health status. EQ-5D and SF-6D measured different things and might not be used interchangeably in COPD patients.
School of Public Health, The University of Hong Kong, Hong Kong, China.
Jing
J
Chen
Department of Family Medicine and Primary Care, The University of Hong Kong, Hong Kong, China.
Carlos K H
CK
Wong
School of Public Health, The University of Hong Kong, Hong Kong, China.
Sarah M
SM
McGhee
Department of Medicine and Geriatrics, Princess Margaret Hospital, Hong Kong, China.
Polly K P
PK
Pang
Department of Medicine and Geriatrics, Princess Margaret Hospital, Hong Kong, China.
Wai-Cho
WC
Yu
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000523:psychology; D019057:Quality-Adjusted Life Years; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards*