α1-Proteinase Inhibitor (Human) in the Treatment of Hereditary Emphysema Secondary to α1-Antitrypsin Deficiency: Number and Costs of Years of Life Gained

David Sclar; Marc Evans; Linda Robison; Tracy Skaer

doi:10.2165/11631920-000000000-00000

Background: α1-Antitrypsin deficiency (α-ATD) is a disorder inherited in an autosomal recessive pattern, with co-dominant alleles known as the protease inhibitor system (Pi). The main function of α1-antitrypsin (α-AT) is to protect the lungs against a powerful elastase released from neutrophil leucocytes. α-ATD typically presents with a serum α-AT level of <50mg/dL. In severe α-ATD, phenotype PiZZ, protection of the lungs is compromised, leading to an accelerated decline in forced expiratory volume in 1 second (FEV1). As a result, a patient may develop pulmonary emphysema of the panacinar type at a young age (third to fourth decades of life), with cigarette smoking being the most significant additional risk factor. It has been shown that weekly or monthly infusion of human α-AT is effective in raising serum α-AT levels to desired levels (>80mg/dL), with few, if any, adverse effects. Objective: The present study was designed to discern the number of years of life gained, and the expense per year of life gained, associated with use of α-AT augmentation therapy (α1-proteinase inhibitor [human]), relative to ‘no therapeutic intervention’ in persons with α-ATD. Methods: Monte Carlo simulation (MCS) was used to: (i) estimate the number of years of life gained; and (ii) estimate the health service expenditures per year of life gained for persons receiving, or not receiving, α-AT augmentation therapy. MCS afforded a decision-analytical framework parameterized with both stochastic (random) and deterministic (fixed) components, and yielded a fiscal risk-profile for each simulated cohort of interest (eight total: by sex, smoking status [non-smoker; or past use (smoker)]; and use of α-AT augmentation therapy). The stochastic components employed in the present inquiry were: (i) age-specific body weight, and height; (ii) age-specific mortality; and (iii) the probability distribution for receipt of a lung transplant, as a function of FEV1. The deterministic components employed in the present inquiry were: (i) age in years for the simulated cohort; (ii) outlays for α-AT augmentation therapy; (iii) health service expenditures associated with receipt of a lung transplant; (iv) annual decline in FEV1; (v) percent predicted FEV1 (vi) initiation of α-AT augmentation therapy as a function of percent predicted FEV1; (vii) need for a lung transplant as a function of percent predicted FEV1; (viii) annual rate of lung infection; and (ix) mortality as a function of percent predicted FEV1. Results are reported from a payer perspective ($US, year of costing 2010). Results: Receipt of α-AT augmentation therapy was associated with a significant increase (p < 0.05) in years of life gained, with female smokers gaining an estimated mean 7.14 years (cost per year: $US248 361 [95% CI 104 531, 392 190]); female non-smokers gained an estimated mean 9.19 years (cost per year: $US160 502 [95% CI 37 056, 283 947)]); male smokers gained an estimated mean 5.93 years (cost per year: $US142 250 [95% CI 48 467, 236 032]); and male non-smokers gained an estimated mean 10.60 years (cost per year: $US59 234 [95% CI 20 719, 97 548]). Conclusion: Use of α-AT augmentation therapy was associated with an increase in years of life gained by sex and history of tobacco use, and at a cost per year of life gained comparable to that of other evidenced-based interventions.

α1-Proteinase Inhibitor (Human) in the Treatment of Hereditary Emphysema Secondary to α1-Antitrypsin Deficiency: Number and Costs of Years of Life Gained

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