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By Gus Cairns and Roger Pebody for NAM AIDSMap
A new study presented at the 19th International AIDS Conference shows that young people, African Americans, and heterosexual men have particularly low rates of retention in care and viral suppression and that there are also inequalities between cities.
A previous study published in November last year had caused concern by revealing that only about half the HIV-positive population of the US was in consistent care and that only 28% had an undetectable viral load.
The US has high rates of HIV testing, but this attrition of treatment, known as the “treatment cascade”, threatens the viability of using widespread antiretroviral therapy as one of the best ways to limit the spread of HIV, as discussed at the IAPAC Controlling the HIV epidemic with antiretrovirals summit in June.
Treatment rates even worse than thought
Irene Hall of the Centers for Disease Control said that the new estimates show that an even lower percentage of people are on treatment and virally suppressed – just a quarter (25%).
The calculations show that an estimated 1.15 million people are living with HIV in the US, of which about 205,000 (18%) remain undiagnosed, and nearly half of whom (45%) are African American, despite their forming only one in eight (12%) of the US population. Just over half (52%) are gay men/men who have sex with men.
Despite their higher prevalence, African Americans are less likely to be virally suppressed (21%), especially concerned with white people (30%). This is due to somewhat lower testing rates and lower rates of linkage to care. It they do see an HIV doctor after diagnosis, black Americans are just as likely to stay in care as white Americans.
Even lower rates of viral suppression were seen in heterosexual men (19% virally suppressed) and especially in younger people: only 15% of people aged 25-34 HIV were on treatment with an undetectable viral load compared with 36% of 55-64-year-olds, though this could be partly due to their being infected more recently and so fewer of them needing to be on ARVs; 24% of people aged 25-34 who were in care were not taking ARVs, compared with 13% of 55-64-year-olds.
Big variations between cities
Another study showed very different results across the continuum of care between four large cities with established HIV epidemics, highlighting the crucial role that state policies on health insurance, the leadership of public health departments and high quality local services can play.
Nanette Benbow found that on four different measures, Chicago and Philadelphia performed relatively poorly, whereas Los Angeles and San Francisco did somewhat better.
For example, in Chicago, just 30% of people previously diagnosed with HIV accessed care in 2009, whereas 57% of those in San Francisco did so. In Chicago, 21% of people with HIV had a suppressed viral load, while 44% of those in San Francisco were undetectable.
There were poorer outcomes for black people, women and the under-30s in some of the cities, but these differences were much less pronounced in San Francisco. In recent years, the city has aggressively promoted HIV testing and early treatment, and put considerable resources into to help patients stay in care and adhere to medication. Outreach teams follow up people who do not show up for appointments and work in co-operation with drug, mental health and housing services to address underlying problems; the outreach work is targeted to neighbourhoods with the greatest needs.
A complex methodology was used to calculate the figures in the case of the CDC study, and Hall told the conference that they might underestimate the proportion of people in care by a few per cent.
Determining HIV prevalence and the proportion undiagnosed is not necessarily an easy thing to do, especially in a federal country like the US with different reporting requirements in different states. Prevalence and linkage to care figures were derived from the country’s National HIV Surveillance System, which gathers name-linked data on HIV cases from 46 states and AIDS data from the others. This system also documents which people have seen an HIV physician for assessment at least once post-diagnosis, which is the definition of linkage to care.
These figures have to be adjusted for delays in reporting new diagnoses and deaths (which mean recent years have to be ‘topped up’) and incomplete reporting of diagnosed cases; one of the most important facts that often goes missing is the route of HIV transmission.
The most uncertain figure is the one for the proportion of people who remain undiagnosed. The way the CDC calculate this is to estimate the average severity of disease at HIV diagnosis, for instance, by taking the proportion of people who have AIDS-defining illness at the time of HIV diagnosis. From this they make a rough back-calculation of the average number of years people have been living with HIV before diagnosis, and from that the number of people living with HIV who remain untested. This is then added to the diagnosed prevalence.
A rough estimate of HIV prevalence is then calculated by taking the cumulative number of reported HIV infections and subtracting from it the reported number of deaths.
‘Linkage to care’ is the proportion of people with at least one CD4 and viral load test result within three months of diagnosis.
‘Retention in care’ and the proportion of people on therapy and virally suppressed was taken from a sample of medical records, from 17 states and the District of Columbia, designed to be representative of the HIV population of the US. Retention in Care was defined as the proportion of adults with HIV who received at least one medical care visit between January and April 2009.
It was commented on at the conference that some people on stable ARV therapy might visit only every six months or so, and people with high CD4 counts who were off therapy even less often.
Hall admitted that this definition of retention in care might underestimate the proportion of people who were regularly attending medical appointments. Certainly, retention in care was the point at which the number of patients remaining in the ‘cascades’ fell of drastically; in many groups of people, only half of those initially linked to care stayed in care.