Testing the Measurement Equivalence of Interactive Voice Response (ivr) and Paper Versions of the Eq-5d

OBJECTIVE: Electronic data capture technologies, such as interactive voice response (IVR) systems, are emerging as important alternatives for collecting patient-reported outcomes data. The objective of this study was to assess the measurement equivalence of an IVR version of the EQ-5D with the original paper version. METHODS: This study utilized a crossover design with subjects randomly assigned to one of two assessment orders: 1) paper then IVR or 2) IVR then paper. A convenience sample of intreatment outpatient cancer clinic patients (n=139) were asked to complete each assessment two days apart. The analyses tested for mean differences (repeated measures ANOVA) and reliability (intraclass correlation coefficient [ICC]) to assess measurement stability over time. Equivalence of the means was established if the 95% confidence interval (CI) of the mean difference was within the minimally important difference (MID) interval: -.035 to .035 for the index and -3 to 3 for the EQ VAS. Adequacy of the ICC was established by comparing the ICC 95% lower CI with a critical value of 0.70. RESULTS: The per protocol analysis included 109 subjects for the EQ VAS and 113 subjects for the index. For the EQ-5D index, the means (SD) of the paper and IVR administrations were 0.790 (0.172) and 0.800 (0.180), respectively. The 95% CI of the mean difference was -0.024 to 0.006, which was within the equivalence interval. The ICC was 0.894 (95% lower CI 0.857), significantly different from 0.70. For the EQ VAS, the means (SD) were 72.0 (19.7) for paper and 74.1 (19.8) for IVR. The 95% CI of the mean difference was -3.784 to -0.484, partially within the equivalence interval. The ICC was 0.897 (95% lower CI 0.859) also significantly different from 0.70. DISCUSSION: This analysis provides evidence that the EQ-5D scores on the IVR version were equivalent to those obtained on the original paper version.