Validation of the EQ-5D quality of life instrument in patients after myocardial infarction

Background: We assessed cross-sectional validity of EQ-5D after myocardial infarction (MI). Methods: We compared EQ-5D, SF-36, quality of life After MI (QLMI), and Canadian Cardiovascular Society Anginal Classification (CCSG) scores. Correlation and regression techniques were used to assess convergent validity. SF-36 and alternate Rand-36 scoring were compared. CCSG class was used to evaluate discriminative validity and clinical difference in health state scores. Results: Of 99 patients: mean age 64; median 176.5 days post-MI; 80% had one MI; 74% were CCSG I. 1/3 to 1/2 reported mobility, self-care, pain, and emotional difficulties on EQ-5D. Median health state was 0.73. EQ-5D and SF-36 (or Rand-36) strongly correlate in overall health (0.75), emotional health (0.75), pain (0.68), and activity/ functional (0.5-0.63). EQ-5D and QLMI strongly correlate in activities/ self esteem (0.56), emotional health (0.64), anxiety/depression -restriction (0.53), and overall health (0.5-0.57). EQ-5D self-care correlates weakly with all domains. Domain scores from each general instrument contributed to each other's overall health score (adjusted R-2 0.61-0.69) and to disease specific score (0.45 adjusted R-2). EQ-5D discriminates among CCSG classes (p < 0.000). Physicians detected a 0.16 difference in health state scores. Conclusion: The EQ-5D provides valid general HrQOL measurement post-MI.