The introduction of antiretroviral treatment (ART, also known as highly active antiretroviral therapy or HAART) in 1996 was a significant moment in the response to HIV. Successful antiretroviral treatment can suppress HIV replication in the body and lower the viral load (amount of virus) in a person’s bodily fluids to undetectable levels. While research has long shown that a lower viral load can improve the health of a person living with HIV, more recent studies have demonstrated that it can also reduce the risk of HIV transmission.
As HIV treatment and prevention have converged, attention has turned to how well people living with HIV are being engaged in the continuum of services needed to achieve an undetectable viral load—including testing and diagnosis, care and support, and treatment. The concept of an HIV treatment cascade, or HIV care cascade, has emerged as a way to identify gaps in the continuum, which are preventing people from realizing the health and prevention benefits of antiretroviral treatment.
In the United States, it is estimated that only 19 to 28% of people living with HIV are on treatment and have an undetectable viral load, suggesting that there are significant gaps in the continuum of HIV services. However, less is known about the treatment cascade in Canada. As a result, researchers in British Columbia decided to characterize the cascade in their province, identify gaps and look at how engagement in the care cascade has changed since antiretroviral treatment first became available in 1996.
Building the cascade
The study investigators constructed a treatment cascade for each year from 1996 to 2011. The cascades show the sequence of steps needed to achieve an undetectable viral load and the proportion of individuals living with HIV who were engaged at each stage. The steps include diagnosis, linkage to care, retention in care, treatment eligibility, initiation of treatment, treatment adherence and virological suppression.
To collect the required information, a recently developed, advanced surveillance system linking data from several sources was used. Data sources included the Public Health Agency of Canada, BC Centre for Disease Control, British Columbia Centre for Excellence in HIV/AIDS and the provincial physician billing database.
Significant gaps were identified in the most recent cascade. Of the estimated 11,700 people living with HIV in 2011, only 4,054 (35%) are thought to have achieved an undetectable viral load. This means that 7,646 people (65%) did not have an undetectable viral load and were therefore not engaged in all of the steps in the cascade.