Comparison of the SF-6D and the EQ-5D in patients with coronary heart disease.
BACKGROUND
The SF-6D was derived from the SF-36. A single summary score is obtained allegedly preserving the descriptive richness and sensitivity to change of the SF-36 into utility measurement. We compared the SF-6D and EQ-5D on domain content, scoring distribution, pre-treatment and change scores.


METHODS
The SF-6D and the EQ-5D were completed prior to intervention and 1, 3, 6 and 12 months post-intervention in a study enrolling 561 patients with symptomatic coronary stenosis. Patients were randomized to off-pump coronary artery bypass surgery (CABG), standard on-pump CABG, or percutaneous transluminal coronary angioplasty (PTCA). Baseline and change over time scores were compared using parametric and non-parametric tests.


RESULTS
The relative contribution of similar domains measuring daily functioning to the utility scores differed substantially. SF-6D focused more on social functioning, while EQ-5D gave more weight to physical functioning. Pain and mental health had similar contributions. The scoring range of the EQ-5D was twice the range of the SF-6D. Before treatment, EQ-5D and SF-6D mean scores appeared similar (0.64 versus 0.63, p = 0.09). Median scores, however, differed substantially (0.69 versus 0.60), a difference exceeding the minimal important difference of both instruments. Agreement was low, with an intra-class correlation of 0.45.Finally, we found large differences in measuring change over time. The SF-6D recorded greater intra-subject change in the PTCA-group. Only the EQ-5D recorded significant change in the CABG-groups. In the latter groups changes in SF-6D domains cancelled each other out.


CONCLUSIONS
Although both instruments appear to measure similar constructs, the EQ-5D and SF-6D are quite different. The low agreement and the differences in median values, scoring range and sensitivity to change after intervention show that the EQ-5D and SF-6D yield incomparable scores in patients with coronary heart disease.
van Stel
Henk F
HF
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, room STR 6.131, PO box 85500, 3584 GA, Utrecht, The Netherlands. h.vanstel@umcutrecht.nl
Buskens
Erik
E
D000368:Aged; D015906:Angioplasty, Balloon, Coronary / Q000523:psychology; D001026:Coronary Artery Bypass / Q000523:psychology; D047549:Coronary Artery Bypass, Off-Pump / Q000523:psychology; D023921:Coronary Stenosis / Q000503:physiopathology* / Q000601:surgery / Q000628:therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011594:Psychometrics / Q000295:instrumentation*; D011788:Quality of Life; D012680:Sensitivity and Specificity; D018434:Sickness Impact Profile; D011795:Surveys and Questionnaires; D013997:Time Factors; D006113:United Kingdom