Testing the measurement equivalence of paper and touch-screen versions of the EQ-5D visual analog scale (EQ VAS)

ObjectivesThis study examined the measurement equivalence of the original paper-based vertical format of the EQ-5D visual analog scale (EQ VAS) with a touch-screen computer-based horizontal format.MethodsA total of 314 subjects were administered two modes of the EQ VAS in a randomized crossover design. One mode was the original paper-based 20 cm vertical EQ VAS; the other mode was touch-screen-based. Measurement equivalence was assessed by testing the 95% confidence interval of the mean differences from an equivalence threshold of −3 to +3 points on the VAS and evaluating the intraclass correlation coefficient (ICC).ResultsThe adjusted mean (SE) EQ VAS score was 80.96 (0.87) on the paper and 79.59 (0.85) on the touch-screen. The mean (CI) difference between scores on the two formats was 1.37 with a confidence interval of 0.175–2.559, wholly contained within the equivalence interval. The ICC was 0.75, indicating acceptable agreement between the two modes. Almost a third (30.1%) of the respondents reported identical scores on both formats.ConclusionThese results provide evidence for the measurement equivalence of this EQ VAS touch-screen administration mode with the original paper mode.