This reports is a detailed case study using a large observational database of patients diagnosed with Rheumatoid Arthritis (n=100,398 observations). Direct estimation of UK EQ-5D scores as a function of Health Assessment Questionnaire (HAQ), pain and age was performed using a limited dependent variable mixture model. And indirect modelling (“response maping”) was undertaken using a set of generalized ordered probit models with expected tariff scores calculated mathematically. Linear regression was reported for comparison purposes.
The report concludes that modelling of EQ-5D from clinical measures is best performed directly using the bespoke mixture model. This substantially outperforms the indirect method in this example. Linear models are inappropriate, suffer from systematic bias and generate values outside the feasible range.
The report, including link is:
M Hernandez Alava, A Wailoo, F Wolfe, K Michaud. A comparison of direct and indirect methods for the estimation of health utilities from clinical outcomes.