Treatment drive in British Columbia produces modest declines in diagnoses and viral loads

Gus Cairns
Published: 19 February 2010

An expansion in the numbers of people with HIV in the Canadian province of British Columbia diagnosed and on treatment has started to produce modest reductions in HIV diagnoses and in the average viral load in the community, the 17th Conference on Retroviruses and Opportunistic Infections (CROI) heard today.

The trends seen were similar to those reported from San Francisco in a similar presentation the previous day – see this report.

In 2008 the health minister for British Columbia announced that the province would pursue an aggressive ‘test and treat’ strategy in order to reap the public health benefit of reducing the average viral load in people with HIV.

However Dr Julio Montaner of the British Columbia Centre for Excellence in HIV/AIDS, the prime mover behind this strategy, told the conference that the ‘second wave’ of increased HAART (highly active antiretroviral treatment) coverage actually started prior to the adoption of this strategy, which in itself does not appear to have further increased access.

Antiretroviral (ARV) coverage started in the province in 1996 and had reached 2500 patients by 1999. After this it reached a plateau. Dr Montaner commented that the steady state observed appeared to be connected to a lot of patients in that era choosing to take treatment interruptions.

Starting from the beginning of 2004, a second wave of treatment uptake began, which continues to this day, and there are now 5000 people in the province on treatment. Many of these people were not drug-naive but re-started treatment after the Centre undertook a campaign of contacting people on treatment interruptions and suggesting they resume.

It is worth noting that there is room for considerable further expansion of treatment in British Columbia, as this figure represents less than half of the estimated number of people who have tested HIV-positive, and a third of the estimated total number of people with HIV.

The proportion of patients on treatment with a viral load under 50 copies/ml increased from 66% in 2000 to 88% in 2008. Montaner commented that concerns had been raised that encouraging people to return to HIV treatment might result in increased drug resistance, as the proportion of patients with poor adherence would increase. In fact, despite this doubling of ARV coverage, the number of new cases of HIV drug resistance declined from 270 in 2000 to 80 in 2008.

Since 2004 there has been a modest, but statistically significant, decline in the number of new HIV diagnoses per year, from 440 in 2004 to 370 in 2009. However this is entirely accounted for by a decrease in diagnoses in injecting drug users (IDUs), which halved during this period, from 150 in 2004 to 80 in 2009.

Montaner said that the reductions appeared to be driven by antiretroviral take-up, rather than changes in risk behaviour, as British Columbia already has a long history of harm reduction schemes for IDUs. The reductions coincided with an outreach campaign to get injecting drugs users on to HIV treatment, though the study could not prove that one caused the other.

The decline in HIV among IDUs was mirrored by a decline in hepatitis C diagnoses in the province. The annual incidence rate in the general population has declined from 0.12% in 1999 to 0.073% in 2004 and 0.055% in 2008. This contrasts with the figures for sexually transmitted infections: syphilis rates have plateaued since 2004 but gonorrhoea and chlamydia rates have continued to climb.

The proportion of non-IDU patients with a viral load under 500 copies/ml increased from 43% in 2004 to 77% in 2009 and the proportion of IDUs from 34% to 74% – nearly the same as other patients. This represents a considerable achievement in a province with a very specific HIV epidemic concentrated in aboriginal Canadians living in remote communities, as well as HIV-positive injecting drug users. Montaner commented that the reductions in viral load were not restricted to Vancouver, but were spread throughout the province.

He also produced an approximate measure of ‘community viral load’: the average viral load within the HIV-positive community at large. Montaner’s way of doing this was to measure the total number of patients ever given a viral load test in the province, minus those known to have died or moved away. This number amounted to 7400 in 2004 and had increased to 10,200 in 2009. He then determined the proportion of tested patients whose viral load was in one of five different viral load strata (under 500, 500 to 3500, 3500 to 10,000, 10,000 to 50,000, and above 50,000) at the end of any given year.

The absolute number of patients with a viral load test result over 500 copies/ml at last test decreased modestly, from 4800 to 4100, between 2003 to 2009, but as a proportion of the total they decreased from 65% to 40%. This represents a rough measurement of the proportion of patients likely to be infectious.

“Our results show an association between expanded HAART coverage, decreased provincial plasma viral load, and decreased new HIV diagnoses,” said Montaner.

“Seek, Test, Treat and Retain (STTR) strategies targeting HIV-positive individuals who meet criteria for HAART initiation should proceed expeditiously,” he added.

Reference

Montaner J et al. Association of expanded HAART coverage with a decrease in new HIV diagnoses, particularly among injection drug users in British Columbia, Canada. 17th Conference on Retroviruses and Opportunistic Infections, San Francisco, abstract 88LB, 2010.

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