Sample size determination for EQ-5D-5L value set studies.

PURPOSE: The EuroQol 5-Dimension (EQ-5D) is a widely used health status instrument for cost-utility analysis of healthcare interventions. Recently, its 5-Level version (EQ-5D-5L) and a protocol for conducting valuation of its health states were developed. We propose four approaches for estimating the sample size for EQ-5D-5L valuation according to the standardized procedures of the protocol.

METHODS: The first approach is for estimating mean health state utility values with a desired precision level using a regression model. The second approach, empirical in nature, determines a sample size based on mean absolute error in predicting health state values using a large-scale reference study. The last two approaches are for assessing the significance of regression coefficients of health state descriptors and to estimate the regression coefficients with a desired precision for predicting health state utility values.

RESULTS: Using data from a Singaporean study, we estimated parameters that are useful for sample size determination, including the design effect. Each of the approaches was illustrated with examples and pragmatic recommendations were provided.

CONCLUSIONS: Capitalizing on the EQ-5D-5L valuation protocol, we proposed four sample size estimation approaches which can help to decide an appropriate sample size for a value set study.