As many as 2500 HIV-positive individuals would become eligible to start antiretroviral therapy (ART) at an annual cost of £25 million once draft guidance recommending ART initiation at 350 cells/mm3 comes into effect, the 14thAnnual British HIV Association (BHIVA) Conference was told last month in Belfast.
There are likely to be both clinical and public health benefits of starting ART at higher CD4 counts, noted Tim Chadborn of the Health Protection Agency (HPA), since transmission may be reduced through a reduction in viral load, but the definition of late diagnosis may have to be revised and treatment costs will increase, he told the conference.
In line with US and European guidelines, draft BHIVA guidelines now recommend starting ART once CD4 counts fall below 350 cells/mm3. Although the primary reason for the recommendation is based on data showing improved clinical outcomes, changing the guidelines on when to start ART will also have public health, policy and surveillance implications.
Tim Chadborn of the Health Protection Agency (HPA) presented data obtained by the HPA from England, Wales and Northern Ireland in order to examine some of the implications of this recommendation being implemented in the UK.
Impact on newly diagnosed individuals and definition of late diagnosis
In 2006, for adults with CD4 counts reported at HIV diagnosis, one third were diagnosed with CD4 counts below 200 cells/mm3, and were considered to have had a late diagnosis.
If the recommended threshold for commencing ART had been 350 cells/mm3, then 57% of all newly diagnosed individuals would have been considered to have been diagnosed late.
In 2007, an estimated 6,840 people were diagnosed with HIV for the first time: 2,257 individuals had a CD4 count below 200 cells/mm3 and 3,899 individuals had a CD4 count below 350 cells/mm3.
Consequently, of the newly diagnosed, an additional 1,642 people would have been considered eligible for starting therapy. “But how many would actually start treatment?” asked Mr Chadborn, “and should we consider these people as having been diagnosed late?”
Impact on people already diagnosed
In 2006, almost 49,000 adults were seen for HIV-related care in England, Wales and Northern Ireland. CD4, viral load and treatment data were available for 39,000 (80%). Of the 11,500 individuals not already on ART, an additional 3060 had CD4 counts between 350 and 200 cells/mm3, and 727 had CD4 counts below 200 cells/mm3.
However, examining the number of individuals who were diagnosed longer than three months and not on ART, this number dropped to 1760 and 216, respectively.
“If these individuals with CD4, VL and ARV are representative of the remaining 20%,” said Mr Chadborn, “then we would expect 2200 with CD4 counts between 350 and 200 cells/mm3 who have been diagnosed more than three months and had never taken ART in 2006.”
However, since around 30% of individuals appear to defer ART despite guidelines recommending they start, he suggested that, “around 1500 might actually have started treatment” if 2006 guidelines had recommended ART at 350 cells/mm3.
Based on current patterns of new diagnoses, he added, “we could expect a potential additional 2500 people requiring treatment according to new guidelines in 2008.”
Possible impact on transmission
Since viral load and likelihood of onward transmission are linked, Mr Chadborn examined the public health impact of individuals with higher viral loads and CD4 counts between 350 and 200 cells/mm3 being eligible for treatment.
He found that a third of individuals (n=1800) not on ART with viral loads over 10,000 copies/ml, and a fifth of individuals (n=895) with viral loads between 500 and 10,000 copies/ml also had CD4 counts between 350 and 200 cells/mm3 and may start therapy earlier due to new guidelines.
Consequently, he found that around 2700 individuals “may have reduced infectivity as a result of starting treatment earlier.”
During the question and answer session that followed, Dr Steve Taylor of Birmingham Heartlands Hospital noted that reduced infectivity depended on a variety of factors, and that if sexual risk-taking increased on a population level, due to perceptions that all ART reduced infectiousness, then this may adversely affect onward transmission.
Conclusions
Mr Chadborn concluded that there are “likely to be both clinical and public health benefits of recommending all HIV-infected persons start ART when they CD4 counts fall to below 350,” including the possibility that onward transmission may be reduced on a population level through a reduction in viral load.
He added that the definition of late diagnosis may have to be revised, but that the focus still needs to be on reducing diagnoses where CD4 counts are below 200 cells/mm3 due to the particularly high risk of mortality at levels below this threshold.
He also noted that treatment costs will increase and said that 1,000 additional adults would cost the NHS an additional £10m per year. However, he concluded, anti-HIV “treatment is cost-effective”.
The draft 2008 BHIVA treatment guidelines are open for consultation until this Friday. Details on how to respond can be found here.
Chadborn T and Delpech V. What are the implications of increasing the recommended threshold for starting anti-HIV therapy (ART)? Fourteenth BHIVA Conference, Belfast. Abstract O20, 2008.