Antiretroviral drug costs and prescription patterns in British Columbia, Canada: 1996-2011.
BACKGROUND
Treatment options and therapeutic guidelines have evolved substantially since highly active antiretroviral treatment (HAART) became the standard of HIV care in 1996. We conducted the present population-based analysis to characterize the determinants of direct costs of HAART over time in British Columbia, Canada.


METHODS
We considered individuals ever receiving HAART in British Columbia from 1996 to 2011. Linear mixed-effects regression models were constructed to determine the effects of demographic indicators, clinical stage, and treatment characteristics on quarterly costs of HAART (in 2010$CDN) among individuals initiating in different temporal periods. The least-square mean values were estimated by CD4 category and over time for each temporal cohort.


RESULTS
Longitudinal data on HAART recipients (N = 9601, 17.6% female, mean age at initiation = 40.5) were analyzed. Multiple regression analyses identified demographics, treatment adherence, and pharmacological class to be independently associated with quarterly HAART costs. Higher CD4 cell counts were associated with modestly lower costs among pre-HAART initiators [least-square means (95% confidence interval), CD4 > 500: 4674 (4632-4716); CD4: 350-499: 4765 (4721-4809) CD4: 200-349: 4826 (4780-4871); CD4 <200: 4809 (4759-4859)]; however these differences were not significant among post-2003 HAART initiators. Population-level mean costs increased through 2006 and stabilized post-2003 HAART initiators incurred quarterly costs up to 23% lower than pre-2000 HAART initiators in 2010.


CONCLUSIONS
Our results highlight the magnitude of the temporal changes in HAART costs, and disparities between recent and pre-HAART initiators. This methodology can improve the precision of economic modeling efforts by using detailed cost functions for annual, population-level medication costs according to the distribution of clients by clinical stage and era of treatment initiation.
*BC Centre for Excellence in HIV/AIDS †Faculty of Health Sciences, Simon Fraser University ‡Division of AIDS, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.
Bohdan
B
Nosyk
Julio S G
JS
Montaner
Benita
B
Yip
Viviane D
VD
Lima
Robert S
RS
Hogg
D000328:Adult; D019380:Anti-HIV Agents / Q000191:economics* / Q000627:therapeutic use; D023241:Antiretroviral Therapy, Highly Active / Q000191:economics / Q000706:statistics & numerical data; D001955:British Columbia / Q000453:epidemiology; D018791:CD4 Lymphocyte Count; D016527:Drug Costs / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000191:economics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D055815:Young Adult
D019380:Anti-HIV Agents