Significant attrition at each step of the HIV care 'cascade' in British Columbia

Patients are being lost at each stage of the HIV care ‘cascade’ in British Columbia, Canada. Investigators from the STOP HIV/AIDS Study group examined data from 1996 to 2011 and estimated the proportion of people engaged with HIV care at each stage of the care continuum, from diagnosis through to viral suppression. Their findings, published in The Lancet Infectious Diseases, show that engagement with care improved steadily over the 15 years of the study. However, there was significant attrition at each stage of the care cascade, and in 2011 only 35% of HIV-positive people had an undetectable viral load.

HIV treatment and care are free in British Columbia (unlike other states in Canada), and the investigators suggest their results “are thus likely to represent a best-case scenario, in which individuals are not subject to financial disincentives and state-of-the-art antiretroviral management is consistently recommended and available”.

The authors of an editorial in the same issue of the journal believe “structural factors embedded in health care systems and stigma and discrimination” are likely explanations for the attrition recorded at each step of the care continuum.

Potent and effective antiretroviral therapy first became available in 1996. Its introduction was accompanied by immediate reductions in rates of serious illness and death among people with HIV. The goal of treatment is suppression of viral load to undetectable levels, thus allowing the immune system to strengthen. There have been significant improvements in HIV treatment and care since 1996. People in resource-rich settings – such as Canada – who are doing well on antiretroviral therapy now have a normal life expectancy. Virally suppressive HIV treatment also has another important benefit, significantly reducing the risk of onward transmission of the virus.

However, large number of people are not benefiting from treatment. Studies from around the world consistently show that a large proportion of HIV-positive individuals are undiagnosed. Moreover, a significant proportion of diagnosed people are not successfully linked to or retained in care, and many do not start or adhere to antiretroviral therapy.

Efforts to reduce the rate of undiagnosed infections and improve engagement with care have become central to strategies to maximise individual and public health benefits of HIV treatment.

Investigators from the STOP HIV/AIDS Study Group wanted to map changes in engagement with care between 1996 and 2011.

They defined eight stages in the care continuum:

• Infection with HIV.
• Diagnosis.
• Linkage to care.
• Retention in care.
• Antiretroviral treatment indicated.
• On HIV therapy.
• Adherent to antiretrovirals.
• Undetectable viral load.

Their calculations regarding the proportion of people engaged in the care continuum were based on sources including province-wide HIV prevalence estimates and population-level data.

A total of 13,140 individuals were diagnosed with HIV over the course of the study. The proportion of HIV-infected population with diagnosed infection increased from 51% in 1996 to 71% in 2011.

But there was significant attrition at each stage in the care continuum. For instance, the proportion of people linked to care was 4% to 10% lower than the proportion diagnosed with HIV. Rates of retention in care lagged behind linkage, reaching a high of 81% in 2011. The proportion of patients indicated for and receiving HIV therapy was close to that retained in care. Among the people taking antiretroviral treatment, the proportion who were adherent to their therapy increased from 76% in 2003 to 87% in 2011.The percentage of people with an undetectable viral load increased from just 0.7% in 1996 to 14% in 2000, and to 35% in 2011.

“We noted substantial improvements in the proportions of people diagnosed, on HAART [highly active antiretroviral therapy], and virologically suppressed,” write the authors. They attribute these gains to increased testing, changes in guidelines concerning the initiation of antiretroviral treatment, improvements in HIV care, and the introduction of more potent and tolerable anti-HIV drugs.

“Careful mapping of the cascade of care is crucial to improve our understanding of how to maximise the beneficial effects of available interventions and to inform efforts to contain the spread of HIV/AIDS,” conclude the authors. “A high-quality HIV surveillance system actively linked to relevant administrative health records is essential for such endeavor.”

The authors of the accompanying editorial argue that “the various cascade steps can jeopardize the health outcomes of many people.” Therefore, it is “important for jurisdictions to develop metrics of treatment cascades and population-based HIV viral load assessments”. They believe the British Columbia study is “an excellent example of the utility of reviewing cascades over time. We look forward to seeing more examples of longitudinal cascade evaluations in the future; shared successes will hopefully help the global community improve the global cascade of HIV care.”