MODELING THE POTENTIAL ECONOMIC-IMPACT OF VIRAL LOAD-DRIVEN TRIPLE-DRUG COMBINATION ANTIRETROVIRAL THERAPY

The purpose of this study is to model the potential economic impact of viral load-driven triple drug combination (including a protease inhib itor) antiretroviral therapy on incremental drug and hospitalisation c osts among individuals with HIV disease. Individuals included in the s tudy were HIV-positive men and women from the province of British Colu mbia, Canada, who were aged 18 years or older and had given consent to access their medical records. The study employed pharmacoeconomic mod elling of drug-and hospital-utilisation patterns among a population-ba sed cohort with free access to antiretroviral therapy. Protease inhibi tor use and associated costs based on actual use in a subsequent perio d was modelled upon men and women who were able to maintain stable CD4 + cell counts (slope greater than or equal to 0) for at least 6 months (baseline period) with an average follow-up period of 30 months (prot ease-like group). A control was modelled upon individuals with declini ng CD4+ cell counts (slope < 0) during similar baseline and follow-up periods. The primary outcome measure was average annual incremental co st of triple drug therapy net of hospitalisation and testing costs in 1996 Canadian dollars ($Can). The utilisation pattern of drugs and hos pitals was modelled from actual use among a total of 1271 individuals who were eligible for this analysis. Programme participants who gave c onsent to access their medical records were more likely to be men (p < 0.001), older (p < 0.020), and on antiretroviral therapy (p < 0.001) than programme participants who did not give consent. No differences w ere observed between the protease-like and comparison groups with resp ect to age (p = 0.65) and CD4+ cell count (p = 0.30) at study entry. O ver a period of 1 year, the protease-like group was shown to spend les s time in hospital (2.7 vs 6.6 days; p < 0.001). This difference in ho spitalisation remained in multivariate models, adjusting for prior AID S-defining illnesses and gender. The average annual incremental cost o f adding a protease inhibitor to a 2-drug antiretroviral regimen was e stimated to be $Can2318 per person. The cost implications of hospital stay while using a protease inhibitor drug and 2 nucleosides translate d into an average annual incremental cost (savings if negative) of bet ween -$Can4798 and -$Can2227 per person. The overall average annual in cremental cost impact per person associated with triple drug therapy w ith a protease inhibitor varied between -$Can2288 to SCan283. Negative incremental costs imply overall savings from adopting triple combinat ion therapy. This modelling exercise demonstrated that the cost of tri ple drug combination antiretroviral therapy with a protease inhibitor among HIV-positive men and women was considerably less than the expect ed acquisition cost of the drug alone due to hospitalisation savings i n the province of British Columbia.