THE COST-EFFECTIVENESS OF OPIOID AGONIST TREATMENT AMONG OPIOID DEPENDENT INDIVIDUALS: EVIDENCE FROM THE REAL-WORLD DATA

Abstract Background Opioid use disorder (OUD) contributes to a heavy burden of disease across the globe, including excessive early mortality and poor quality of life. Methadone and buprenorphine are classified by the World Health Organization (WHO) as Essential Medicines as opioid agonist treatment (OAT) of OUD1. Although evidence showed OAT substantially reduces all-cause mortality among people with OUD2, the cost- effectiveness of OAT should be further evaluated. For the evaluation of health utility difference, one optimal measure is health benefit in terms of quality-adjusted life year (QALY), of which both survival and quality of life (QoL) are taken into consideration. Also, it will be more suitable to take a lifetime perspectives accounting for both life expectancy and QoL when capturing the health impact of OAT on opioid-dependent individuals. Aims & Objectives We first estimated the life expectancy (LE) and loss of life expectancy (loss-of-LE) from an OUD cohort stratified by OAT for comparison, then attempted to quantify the difference in loss of quality-adjusted life expectancy (QALE) for demonstration the health utility gain by OAT. The lifetime medical costs were then calculated using the National Health Insurance (NHI) database in Taiwan. We evaluated the cost-effectiveness of OAT versus non-OAT treatment by integrating a survival function with mean-cost over a lifelong horizon. Methods A total of 1283 participants with OUD recruited in the beginning of OAT implementation were linked to the National Mortality Registry for 8 years with stratification by OAT. Kaplan-Meier estimation for survival was performed, and it was extrapolated to 70 years to obtain the LE using a semi-parametric method. We further estimated the loss-of-LE for both cohorts by subtracting their life expectancies from the age- and sex- matched referents of the general population. Cause-specific standardized mortality ratios (SMRs) were calculated and compared with the national cohort to validate the representativeness of this sample. Then, a subsample of subjects' quality of life with EQ-5D was collected for utility values and multiplied by survival functions to estimate the QALE, while that for the age- and sex-matched referents were adjusted to the value collected from the 2009 National Health Interview Survey, and the difference between them was the loss-of-QALE. Finally, we linked the medical claims of NHI datasets with the survival function to estimate the mean cumulative costs since the first date of their diagnosis then extrapolate to lifetime healthcare expenditure of both the OAT/non-OAT cohorts. Results Both survival and QOL of the OAT group were significantly better than those of the non-OAT group. After lifetime extrapolation, the estimated QALE and loss-of-QALE were 17.8 and 18.2 QALY for OAT subjects, respectively, while those of the non-OAT group were 9.2 and 27.9 QALY. The incremental cost- effectiveness ratio (ICER) of OAT versus non-OAT group were US$1,808 per life-year saved and US$1,454 per QALY saved, respectively. Discussion & Conclusion Take cost-effectiveness into consideration, OAT should be further promoted for opioid-dependent population. References 1.World Health Organization. 2005. WHO Model List of Essential Medicines 14th Edition. http://whqlibdoc.who.int/hq/2005/a87017_eng.pdf. Accessed February 2009. 2.Sordo L, Barrio G, Bravo MJ, Indave BI, Degenhardt L, Wiessing L, Ferri M, Pastor-Barriuso R. 2017. Mortality risk during and after opioid substitution treatment: systematic review and meta-analysis of cohort studies. BMJ. DOI: 10.1136/bmj.j1550.