I feel like a broken record here – sorry in advance for those who already knew this.
Another paper has:
(1) Talked about putting “Death” in as a state to anchor DCE estimates to get proper QALY values, (although thankfully they didn’t do it in their study, but even saying it is a possible solution is wrong)
(2) Not done a proper literature review. I, together with Tony Marley (who, together with Duncan Luce, axiomatized random utility theory independently of McFadden), debunked that in 2008, and in 2010 I gave the potential solutions in a paper in Pharmacoeconomics.
Can we move on please? From discussions I get the impression the EuroQoL Group understand this – plus they have funded a group of us to test one of my solutions. But there are other groups out there who aren’t up to speed.
For the Japanese group, I’ll just pose a question to a hypothetical scenario that, I hope, will make clear just why the “death state” thing is wrong.
Suppose you have a group of people who for whatever reason (perhaps religious) never pick “death” in preference to a health state.
QUESTION: What happens when you estimate a conditional logit model to get QALY weights?
If you counter with “there are always people who consider some states worse than death and then you can estimate the model, I’d suggest you go read Thurstone, Luce & Marley, and then the Louviere/Hensher stuff. A DCE is, technically, a model of THE INDIVIDUAL. You should, in principle, be able to estimate a model for an individual (if you give them enough choices – of course in practice we typically can’t but you should be able to in theory if your model really is a DCE i.e. rooted in random utility theory).