COST-effectiveness of salmeterol/fluticasone propionate combination (Advair®) in uncontrolled asthma in Canada
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OBJECTIVE: To evaluate the cost-utility of the treatment with a long acting beta-agonist (LABA) and inhaled corticosteroid (ICS) combination inhaler [salmeterol xinafoate (SAL)/fluticasone propionate (FP) combination inhaler (SFC) (Advair(®))] to continuing on current ICS dose (no ICS dose change) or increased ICS dose [fluticasone propionate (FP)] in patients with uncontrolled asthma in Canada. METHODS: A cost-utility analysis was conducted from a Canadian public healthcare perspective with a one year time horizon. In the no FP dose change scenarios, remaining on daily low (FP 100 ug BID) or medium (FP 200-250 ug BID) or high dose (FP 500 ug BID) was considered. In the increased FP dose scenarios, doubling the FP dose from low to medium dose and from medium to high dose regimens were considered. A decision model was developed with two health states: "symptom free" or "with symptoms". Clinical efficacy was based on a meta-analysis of relevant randomized controlled trials. Over the one year time horizon the percentage with symptom free days (SFD) was used as the measure of differential treatment scenario effectiveness. Drug costs and non-drug costs were incorporated into the analysis. Utilities, derived from EQ5D scores and health services resource use based on patient diaries for 'symptom free' and 'with symptoms' were based on regression analyses of individual patient data from the Gaining Optimal Asthma controL (GOAL) trial. Costs were assessed by assigning unit cost for each health services resource use for each patient. The incremental cost-utility ratios (ICUR) for SFC vs no FP dose change or increased FP dose were estimated using descriptive statistics. Uncertainty was assessed by deterministic and probabilistic sensitivity analysis (PSA). RESULTS: Over one year, SFC resulted in an incremental cost per patient of $544-$655 compared to no FP dose change and $47-$380 per year compared to increased FP dose. SFC results in incremental QALYs per patient of 0.0100-0.0149 compared to no FP dose change and 0.0136-0.0152 compared to increased FP dose. The one year ICURs were $43,000 to $54,400 per QALY gained for SFC compared to no FP dose change and $25,000 to $3500 per QALY gained compared to increased FP dose scenarios. The probability of SFC being cost-effective at $50,000 per QALY gained was greater than 75% compared to increased FP dose scenarios and compared to no dose change for patients on low or medium dose FP. The results were robust to changes in assumptions within the model. CONCLUSION: In Canadian patients with inadequately controlled asthma on FP, it is cost-effective to use SFC for patients 12 years and over compared to doubling their FP dose. It is also cost-effective to use SFC for patients on low or medium dose FP compared to remaining on the current FP dose in patients with uncontrolled asthma.