To assess the measurement equivalence of an interactive voice response (IVR) version of the EQ-5D with the original paper version.
Subjects were randomly assigned to: 1) paper then IVR, or 2) IVR then paper and asked to complete the questionnaire two days apart. The analyses tested mean differences (repeated measures analysis of variance) and reliability (intraclass correlation coefficient [ICC]). Equivalence of the means was established if the 95% confidence interval (CI) of the mean difference was within the minimally important difference interval: −0.035 to 0.035 for the EQ-5D index and −3 to 3 for the visual analog scale (EQ VAS). ICC adequacy was tested by comparing the ICC 95% lower CI with a critical value of 0.70.
The analyses included 113 subjects for the index and 109 subjects for the EQ VAS. For the index, the adjusted means of the paper and IVR versions were 0.789 ± 0.016 and 0.798 ± 0. 017, respectively. The 95% CI of the mean difference was −0.024 to 0.006, within the equivalence interval. The ICC was 0.894 (95% lower CI 0.857), significantly greater than 0.70. For the EQ VAS, the adjusted means were 71.94 ± 1.87 for paper and 74.63 ± 1.79 for IVR. The 95% CI of the mean difference was −4.347 to −1.049, partially within the equivalence interval. The ICC was 0.887 (95% lower CI 0.840), significantly greater than 0.70.
The results provide evidence that the EQ-5D scores on the IVR version were sufficiently equivalent to those obtained on the paper version.