Dear all,

I have been asked to look into a health economics model over a period of 5 
years. There are two groups, a  Standard care and a treatment group.  My 
colleague asked for advice on how we could look at the issue of responders 
and non responders and the associated costs and QALYs, and then CQG, cost 
per qaly gained (difference in costs / difference in Qalys).  The theory 
being that this would give a clearer picture of what really happens in 
clinical practice.

For each group, treatment and standard care, the model calculates the 
average total costs and QALYs per patient over the five years for each of 
the groups and then calculates the GQG of treatment vs. standard care.

We want a method for looking further into the model by looking at responders 
and non responders because the responders are generally better off and thus 
incur less direct costs, wheras the non responders don’t incur as many 
treatment costs because they are taken off treatment if they don’t respond 
within 2 years, but then their course of disease progression is worse.

A patient in the treated group is reviewed at the end of year 2, the patient 
in the treatment group is classed as a responder or a non-responder.  If 
they have not responded then they do not receive any further treatment and 
the disease takes its natural course, i.e standard care. Otherwise they 
continue the treatment leg.

What comparisons can be made?????

MODEL1 One argument is that clinical practice or the budgeting for treatment 
in NHS would be mirrored by treatment costs being the responders costs over 
the five years and the non responders costs over the first two years.
The non treatment costs will be costs for the standard care group plus the 
costs from year 3 to 5 at ‘standard care’ (this is the group of non 
responders that now behave like a patient in the standard care group).  
QALYs could be calculated in a similar manner and the two groups can be 
compared somehow to get a CQG estimate.

MODEL2 Another argument is that the only way to model such an idea is to 
keep the treatment and standard care groups separate and do an ‘ITT’ type 
analysis, so , although the non responders no longer have treatment after 
two years they are still incurring costs and QALYs for the treatment group 
(even though they behave as the standard care group).  A CQG of treatment 
vs. standard can then be calculated.

I believe that the problem with model 1 is that the cost and QALYs can’t be 
combined for responders and non responders to get a CQG comparison to 
treatment costs vs. standard care because of the difference in the number of 
years the QALYs and costs are calculated over.  I do not think this model 
would be valid, to me it does not make logical sense because the outcome is 
not clear as to whether we are looking at treatment vs. standard care groups 
of treatment vs non treatment costs.  However, if the methodology is o.k, 
how should the groups becompared and what should be done?

Model 2 I think is a valid way of making a treatment group versus standard 
care group because both costs and QALYS span the ten year period and so are 
easy to compare.  The question is whether this models clinical practice.  
The argument I have had put to me is that this method more mirrors a 
clinical trial.

Does anyone have any references that might be of use?  Or any other 
suggestions on how this issue could be used to mirror clinical practice? or 
general comments on validity?

Thanks
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