Economic and epidemiological modelling of full-length antihaemophilic factor (recombinant), plasma/albumin-free method, in previously treated patients with haemophilia A : comparison with B-domain deleted rFVIII, and value of potential viral transmission reduction due to plasma/albumin-free status.

OBJECTIVE

To the extent that current recombinant clotting factor concentrates contain even trace amounts of human or animal protein, there is continuing potential for transmission of nonenveloped viruses, including hepatitis A, and parvovirus, and the theoretical potential for transmission of relatively unknown agents, such as prions (Creutzfeldt-Jakob disease, or its variant). Full-length antihaemophilic factor (recombinant), plasma/albumin-free method (rAHF-PFM; Advate), represents a novel pharmacotherapeutic option for the management of haemophilia A. This investigation was designed to discern: (i) the efficacy-based use pattern (International Units [IUs]) of rAHF-PFM versus B-domain deleted rFVIII (BDDrFVIII; ReFacto) required to resolve a bleeding episode (event) among previously treated patients with haemophilia A employing on-demand treatment; (ii) the health service expenditure pattern (percentage differential; payor's perspective) associated with use of rAHF-PFM versus BDDrFVIII among previously treated patients with haemophilia A employing on-demand treatment; and (iii) the fiscal utility attributable to the plasma/albumin-free status of rAHF-PFM under the assumed emergence of a novel and infectious blood (plasma)-borne virus.

METHODS

Data stemming from phase II/phase III clinical trials of rAHF-PFM, together with published literature on BDDrFVIII, afforded calculation of the probability of occurrence for specific endpoints of interest (e.g. non-response to first infusion). Monte Carlo simulation, a decision-analytical framework parameterised with stochastic (random) and deterministic (fixed) components (10 000 iterations per month [or year] of age examined [3, 6, 9 months; years 1 through 19; and years 20, 30, 40, 50, 60, 70 and 80]) was used to compare: (i) the efficacy-based use pattern by treatment option; and (ii) the health service utilisation-based expenditure pattern by treatment option, accounting for the need for subsequent infusion(s), and potential complications (use of services) stemming from failure of the initial infusion (five scenarios). Theoretical and direct modelling methods for assessing the fiscal utility attributable to the plasma/albumin-free status of rAHF-PFM under the assumed emergence of a novel and infectious blood (plasma)-borne virus were developed. Assumptions included: (i) a low population infection rate (<5%); (ii) annual health service expenditures equivalent to 5% of that observed with HIV/AIDS; and (iii) the number of bleeding events experienced per year were 6, 9 or 12.

RESULTS

Monte Carlo simulation-replicated simulations per year of age examined revealed: (i) use of rAHF-PFM resulted in a 12.20% median reduction in the number of IUs required to resolve a bleeding episode (event) relative to BDDrFVIII (p < 0.05); and (ii) a health service utilisation-based savings [primary care; hospital] (p < 0.05; range 13.74-39.34% [dependent on intensity (sequencing) of care required]) with rAHF-PFM relative to BDDrFVIII. The overall scenario-weighted health service utilisation-based savings was 16.94% (p < 0.05). Under the assumption of the emergence of a novel and infectious blood (plasma)-borne virus, deterministic models for persons weighing 20 kg, 50 kg and 80 kg all revealed a savings potential ($US per IU) with use of rAHF-PFM relative to use of a non-plasma/albumin-free product.

CONCLUSIONS

Use of rAHF-PFM in on-demand management of haemophilia A offers enhanced patient safety and represents a fiscally prudent therapeutic strategy.