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.
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
Henk F
HF
van Stel
Erik
E
Buskens
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