Comparing the EQ-5D 3L and 5L: measurement properties and association with chronic conditions and multimorbidity in the general population

Background: Studies comparing the measurement properties of EQ-5D 3L (3L) and EQ-5D 5L (5L) are limited to specific patient populations with small sample sizes. Using a general population sample, we compared 3L and 5L in terms of their measurement properties and association with number of chronic conditions, including multimorbidity - the concurrent occurrence of two or more chronic conditions. Methods: Data were available from two consecutive cycles of a cross-sectional telephone interview survey using 3L (2010 cycle) and 5L (2012 cycle), in the general population of adults (age >= 18 years) in Alberta, Canada. Measurement properties were compared by determining their feasibility, ceiling effect, and discriminatory power (Shannon indices) for 3L and 5L. Linear regression models were fitted to test the associations between multimorbidity and EQ-5D index score. Results: Data were available for 4946 (2010) and 4752 (2012) survey respondents with information on HRQL. Compared to 3L, 5L showed lower ceiling effect (32.3% versus 42.1%), higher absolute discriminatory power (Shannon index, mean 0.79 versus 0.52) and higher relative discriminatory power (Shannon Evenness index, mean 0.09 versus 0.06 for 3L). Despite these differences, similar relationships of lower HRQL with greater multimorbidity were observed for the 3L (beta = -0.13, 95% CI -0.15; -0.11) and 5L (beta = -0.12, 95% CI -0.13; -0.11). Conclusions: Using a general population sample, the EQ-5D 5L showed better measurement properties than the EQ-5D 3L. Nonetheless, clinically important differences in HRQL associated with multimorbidity were similar in magnitude using both versions of EQ-5D.