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. 2010 Aug 14;376(9740):532-9.
doi: 10.1016/S0140-6736(10)60936-1. Epub 2010 Jul 16.

Association of highly active antiretroviral therapy coverage, population viral load, and yearly new HIV diagnoses in British Columbia, Canada: a population-based study

Julio S G Montaner  1 , Viviane D Lima, Rolando Barrios, Benita Yip, Evan Wood, Thomas Kerr, Kate Shannon, P Richard Harrigan, Robert S Hogg, Patricia Daly, Perry Kendall
Affiliations

Association of highly active antiretroviral therapy coverage, population viral load, and yearly new HIV diagnoses in British Columbia, Canada: a population-based study

Julio S G Montaner et al. Lancet. .

Abstract

Background: Results of cohort studies and mathematical models have suggested that increased coverage with highly active antiretroviral therapy (HAART) could reduce HIV transmission. We aimed to estimate the association between plasma HIV-1 viral load, HAART coverage, and number of new cases of HIV in the population of a Canadian province.

Methods: We undertook a population-based study of HAART coverage and HIV transmission in British Columbia, Canada. Data for number of HIV tests done and new HIV diagnoses were obtained from the British Columbia Centre for Disease Control. Data for viral load, CD4 cell count, and HAART use were extracted from the British Columbia Centre for Excellence in HIV/AIDS population-based registries. We modelled trends of new HIV-positive tests and number of individuals on HAART using generalised additive models. Poisson log-linear regression models were used to estimate the association between new HIV diagnoses and viral load, year, and number of individuals on HAART.

Findings: Between 1996 and 2009, the number of individuals actively receiving HAART increased from 837 to 5413 (547% increase; p=0.002), and the number of new HIV diagnoses fell from 702 to 338 per year (52% decrease; p=0.001). The overall correlation between number of individuals on HAART and number of individuals newly testing positive for HIV per year was -0.89 (p<0.0001). For every 100 additional individuals on HAART, the number of new HIV cases decreased by a factor of 0.97 (95% CI 0.96-0.98), and per 1 log(10) decrease in viral load, the number of new HIV cases decreased by a factor of 0.86 (0.75-0.98).

Interpretation: We have shown a strong population-level association between increasing HAART coverage, decreased viral load, and decreased number of new HIV diagnoses per year. Our results support the proposed secondary benefit of HAART used within existing medical guidelines to reduce HIV transmission.

Funding: Ministry of Health Services and Ministry of Healthy Living and Sport, Province of British Columbia; US National Institute on Drug Abuse; US National Institutes of Health; Canadian Institutes of Health Research.

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Conflict of interest statement

Conflict of Interest: Dr. Montaner is supported by the Ministry of Health Services and the Ministry of Healthy Living and Sport, from the Province of British Columbia; through a Knowledge Translation Award from the Canadian Institutes of Health Research (CIHR); and through an Avant-Garde Award (No. 1DP1DA026182-01) from the National Institute on Drug Abuse, at the US National Institutes of Health. He also received funding from Merck, Gilead and ViiV Healthcare to support research into Treatment as Prevention. Dr. Harrigan holds the GlaxoSmithKline/Canadian Institutes of Health Research Chair in Clinical Virology. Dr. Kerr is supported by the Canadian Institutes for Health Research and the Michael Smith Foundation for Health Research. Dr. Lima is supported through Fellowship Awards by Canadian Institutes of Health Research and Michael Smith Foundation for Health Research. The study was further supported by the US National Institutes of Health (R01DA021525) and the Canadian Institutes of Health Research (MOP-79297, RAA-79918). Drs. Hogg and Harrigan have received honorariums, travel grants to attend conferences and research grants from pharmaceutical companies working in the area of HIV/AIDS. Drs. Lima, Kerr, Wood, Shannon, Barrios, Daly, Kendall and Ms. Yip declare no conflicts.

Figures

Figure 1
Figure 1
a. Number of active highly active antiretroviral therapy (HAART) participants in the British Columbia Centre for Excellence in HIV/AIDS and number of New HIV-positive diagnoses per year in British Columbia from 1996 to 2009. p refers to the p-value for trend obtained from the generalized additive model. IDU refers to those individuals who have ever injected illicit drugs. b. Number of New HIV-positive diagnoses (blue = observed, red = expected) per year in British Columbia during the three phases of the study period, from 1996 to 2009. The p-values refer to the total observed number of HIV-positive diagnosis (blue square) compared to the total expected number of HIV-positive diagnosis (red square) at the end of each of the 3 time periods.
Figure 1
Figure 1
a. Number of active highly active antiretroviral therapy (HAART) participants in the British Columbia Centre for Excellence in HIV/AIDS and number of New HIV-positive diagnoses per year in British Columbia from 1996 to 2009. p refers to the p-value for trend obtained from the generalized additive model. IDU refers to those individuals who have ever injected illicit drugs. b. Number of New HIV-positive diagnoses (blue = observed, red = expected) per year in British Columbia during the three phases of the study period, from 1996 to 2009. The p-values refer to the total observed number of HIV-positive diagnosis (blue square) compared to the total expected number of HIV-positive diagnosis (red square) at the end of each of the 3 time periods.
Figure 2
Figure 2
Distribution of annual pre-HAART CD4 cell count (cells/mm3) for all individuals initiating HAART in British Columbia from 1996 until 2009. Median yearly baseline CD4 cell counts are listed below the horizontal axis and illustrated (X) on the plot.
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