OBJECTIVES

To investigate the impact of the baseline strategy on the cost-effectiveness results, when a sequence of treatments is used.

METHODS

We reviewed submissions to the UK National Institute for Health and Care and Excellence (NICE) to understand how economic models that used comparisons of treatment sequences defined the baseline strategy. We then built a simple Markov model to use as a case study. The analysis we conducted contained four hypothetical treatments of varying cost-effectiveness relationships to a fixed control (best-supportive care): TxA was cost effective, TxB was extendedly dominated by TxA, TxC was cost-effective, but had a greater cost than both TxA and TxB, and TxD was not cost-effective.

RESULTS

Our review of the NICE submissions showed that, in most cases, authors relied on clinical guidelines, expert opinion or previously developed models to define the baseline strategy (n=31). In several cases the choice of a baseline strategy was not explained (n=9). Several studies used the model to identify the optimal position for the new intervention (n=5). Using the model, all possible permutations between the hypothetical treatments were generated and ranked by their net monetary benefit (NMB). We showed that (i) a non-cost-effective treatment would never be part of an optimal sequence and (ii) the choice of baseline treatment sequence can change the cost-effectiveness estimate of a new intervention.

CONCLUSIONS

If the aim of the decision maker is the efficient distribution of health-care resources based on cost-effectiveness, then the baseline strategy should be created based on the ranking of the NMB. Ignoring the cost-effectiveness of individual treatments when defining the baseline strategy, may lead to spurious results.