The model used the estimate of RR (0.6), a 10% variation in RR (0.54–0.66) estimated the ICER in the range –£3431 to –£1923 which gives the robust result for the dominant strategy. Figure 3. Tornado diagram. A two-way sensitivity analysis showed comparable results. Nearly all of the estimates of ICER were negative as shown in Table 5. The two-way sensitivity analysis of two main input drivers also showed robust ICER estimates of the ethyl-EPA as an adjunct therapy of bipolar disorder. Table 5. Two-way sensitivity analysis: (i) cost of stable state (ii) utility of stable state. There is uncertainty

associated with the estimates of inputs and the health related data. PSA takes into account Inhibitors,research,lifescience,medical uncertainty by assigning distributions to the input variables. The characteristics of cost data are represented by gamma distribution, transition probabilities and health-state Small molecule library supplier utilities are represented by Inhibitors,research,lifescience,medical beta distributions. A total of 10,000 simulations of the model are run on MS Excel, the PSA findings are presented in a cost-effectiveness acceptability curve (CEAC) shown in Figure 4. Figure 4. Cost-effectiveness acceptability curve (CEAC). The CEAC shows the percentage of simulations which are cost-effective at different willingness-to-pay Inhibitors,research,lifescience,medical (WTP) levels. As we are assuming NHS perspective which is the direct payer (although

some of the informal care costs are Inhibitors,research,lifescience,medical also added), the lower NHS threshold of £20,000 has 94.67% probability for the ethyl-EPA as an adjunct treatment to be cost-effective. The high probability of cost-effectiveness was expected as the estimated ICER is also negative suggesting a dominant strategy. The mean ICER of 10,000 simulations

is –£2421. Discussion The results of the model and sensitivity analysis present a strong case for the cost-effectiveness of ethyl-EPA as an adjunct treatment for BD. Ethyl-EPA was dominant in that it resulted in lower costs and better outcomes than the placebo. Other modelling studies have produced evidence of cost-effectiveness for haloperidol in the treatment of mania and to some extent Inhibitors,research,lifescience,medical olanzapine [Bridle et al. 2004], olanzapine maintenance treatment for bipolar disorder [McKendrick et al. 2007], and lamotrigine compared with olanzapine, lithium, and no treatment [Calvert et al. Histone demethylase 2006]. To aid the development of clinical guidelines for bipolar disorder in the UK a Markov model was constructed to compare drug treatments and this found that valproate dominated olanzapine [National Collaborating Centre for Mental Health, 2006]. A similar model was developed by Soares-Weiser and colleagues and this found valproate to be the least expensive nondominated treatment for patients who had recently experienced a depressive episode [Soares-Weiser et al. 2007]. For those who had had a manic episode, olanzapine dominated all other treatments except for lithium.