The minimum clinically important difference for EQ-5D index: a critical review.

The European Quality of Life-5 Dimensions Questionnaire (EQ-5D) is the most common instrument to value health outcomes under the patient's perspective. Several studies have investigated whether observed changes are meaningful to patients, using a variety of approaches to estimate the minimum clinically important difference (MCID). This study provides an overview of the state of art of the estimation of the MCID for the three-level EQ-5D index based on the UK scoring algorithm, critically assessing the available evidence. The interest in estimation of MCID for the EQ-5D has been increasing in recent years. However, some additional standardization in the estimation procedures may be of value, in order to enhance the ability to make comparisons across measures and disease areas. Further methodological research might also contribute to reducing gaps between theory and practice.