Cost-effectiveness and cost-utility analysis of tiotropium treatment for Bronchiectasis: Evidence from a cross over randomised trial

Aim: The aim of this study is to determine the relative cost-effectiveness of administering tiotropium compared to a placebo in adult patients with non-cystic fibrosis (CF) bronchiectasis with airflow obstruction, from a funder perspective. Methods: Clinical efficacy data was obtained from a randomised placebo-controlled crossover study of tiotropium treatment in adult patients with stable, non-CF bronchiectasis in combination with aggregated hospital costs and cost of health services (NZ, 2016) obtained via self-reported health utilisation data. A decision tree/Markov model consisting of patient transition and outcomes was developed. A cost-effectiveness and cost-utility analysis was performed to produce incremental cost-effectiveness ratios (ICERs) and reported in costs per exacerbation avoided and costs per quality-adjusted life-years (QALYs) gained. Sensitivity and scenario analyses were also conducted to test the robustness of outcomes illustrated by using cost-effectiveness acceptability curves against a willingness-to-pay threshold (WTP) and identifying the conditions in which tiotropium could be cost- effective for bronchiectasis patients. The WTP threshold was based on the Gross Domestic Product (GDP) per capita as recommended by the World Health Organization (WHO). Results: There were no significant differences between costs and outcomes for treatment and control arms. The mean (Standard error) number of exacerbations was 1.2 (0.12) for tiotropium and 1.23 (0.11) for the placebo; the mean QALYs was 0.88 and 0.87 respectively. First year costs per patient were NZD 641 (95% CI $583, $702) for tiotropium (TI) and NZD 503 (95% CI $430, $585) for placebo (PL) treatment in the year 2016. Patients treated with tiotropium gained 0.62 (95% CI 0.58, 0.65) quality adjusted life years compared to 0.59 (95% CI 0.56, 0.62) QALYs for the placebo. In incremental terms, TI gained additional QALYs of 0.03 units and 0.01 of exacerbation events at an incremental cost of NZD 137 resulting in the cost per exacerbation avoided of NZD 12,896 (95% CI $5,850, $15,300) and the cost per QALY gained of NZD 4,655 (95% CI $3,900, $7,650). The reported incremental cost effectiveness ratios are well-below the willingness-to-pay threshold for New Zealand (~ NZD 40,000). Conclusion: The results from this study show that tiotropium may be cost-effective compared to a placebo, particularly in terms of improving QALYs, but less likely in respect of reducing exacerbations. Sensitivity analysis suggests that favourable outcomes may be linked to patients with moderate to severe bronchiectasis. Further studies are required before a more definitive answer can be reached