EQ-5D is a standardized instrument developed by the EuroQol Group as a measure of health-related quality of life that can be used in a wide range of health conditions and treatments. The EQ-5D consists of a descriptive system and the EQ VAS. The descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression on a scale ranging from 1 (no health state problem) to 3 (extreme health state problems). The EQ VAS records the patient's self-rated health on a vertical visual analogue scale ranging from 0, worst health state, to 100, best health state. A scoring function is used to assign a value (i.e., EQ-5D™ index score) to self-reported health states from a set of population-based preference weights. For the U.S. general population, the possible EQ-5D index scores range from -0.11 to 1.0 where 0.0 = death and 1.0 = perfect health.