Table 2.

Different potential versions of cost-equivalence

Variants of cost-equivalence
Pure cost equivalence (CE)	Where PHS is prepared to provide treatment A, provide reasonable substitute treatment B iff CostB is ≤CostA
Cost-effectiveness equivalence (CEE)	Where PHS is prepared to provide treatment A, provide substitute treatment B iff CostB is ≤CostA and CostB/QALYB ≤ CostA/QALYA*
Cost-effectiveness threshold equivalence (CETE)	Where PHS is prepared to provide treatment A, provide substitute treatment B iff CostB is ≤CostA and CostB/QALYB is ≤Cost Effectiveness Threshold**
Refusal cost-equivalence (RCE)	Where the cost of refusing treatment is >cost of optimal treatment A, and a PHS is prepared to absorb the costs of refusing treatment A, provide substitute treatment B iff CostB is ≤Costrefusal

* Substitute treatments can be more cost effective but still sub-optimal if they are less effective overall (and cheaper), or where there is uncertainty about effectiveness eg Cytisine

** The reason for restricting CEE and CETE to treatments that are less expensive than the optimal treatment is because this ensures no negative impact on overall health budgets, and Pareto optimality. Permitting requests for substitute treatment that are more expensive than the optimal treatment (albeit within the ICER threshold) would lead to increased health expenditure