Background: As part of the Affordable Care Act, health utility metrics are being investigated to define a cost-effective, value-based health care model. EuroQOL-5D (EQ-5D) and Short Form-6D (SF-6D) are commonly used quality-of-life instruments. Domains in the EQ-5D questionnaire are thought to be less responsive in measuring quality of life after cervical surgery.
Objective: To evaluate the validity and responsiveness of SF-6D and EQ-5D in determining health and quality of life after elective cervical spine surgery.
Methods: A total of 420 patients undergoing elective cervical spine surgery over a period of 2 years were enrolled in a prospective longitudinal registry. Patient-reported outcomes Neck Disability Index (NDI), EQ-5D, and SF-12 were recorded. Based on previously published equations, SF-6D was calculated using NDI and SF-12 scores. Patients were asked whether "surgery met their expectations" (meaningful improvement). The validity and relative responsiveness of SF-6D (NDI), SF-6D (SF-12), and EQ-5D to discriminate between meaningful and nonmeaningful improvement were calculated.
Results: Sixty-six percent of patients (277) reported a level of improvement after surgery that met their expectations (meaningful improvement). SF-6D (NDI) (area under the curve [AUC] = 0.69) was a more valid discriminator of meaningful improvement compared with the SF-6D (SF-12) (AUC = 0.65) and EQ-5D (AUC = 0.62). SF-6D (NDI) was also a more responsive measure compared with SF-6D (SF-12) and EQ-5D (standardized response mean difference: 0.66, 0.48, and 0.44, respectively).
Conclusion: SF-6D is a more valid and responsive measure of general health and quality of life compared with EQ-5D. SF-6D derived from disease-specific disability scores was more valid and responsive than that derived from the generic preference-based SF-12. Cost-effective studies should use SF-6D as a measure of QALY after cervical spine surgery.