researchers first looked at general diagnosis and viral load trends between
2001 and 2011. The total number of people in HIV care in Calgary doubled in this
time, from 757 to 1423. The proportion on ART increased from 62 to 81%, and the
proportion with viral loads under 50 copies/ml doubled from 32 to 66%.
the rate of new diagnoses increased from 4.4 to 5.8% a year and the mean viral
load per patient in care did not significantly change: it was 32,000 copies/ml in 2001
and 30,000 copies/ml in 2010.
first sight this seems a paradoxical result: how can the average viral load stay the same while the proportion who are undetectable doubles? The
answer is that as the proportion in regular care who are
virally suppressed increases, so the people who are not virally suppressed
are ever more likely to be those who are newly diagnosed or not in regular care.
examine exactly which people have detectable viral loads, the researchers
took a closer look at everyone seen for care in 2009 at the Calgary clinic
and split them into six groups. In all groups, average viral load was the mean
of all viral load tests taken during 2009; people with an undetectable viral load were treated
as having viral loads of 50 copies/ml exactly, so someone with several viral
load tests would have to be undetectable in all of them to be classed as having a mean viral load of 50 copies/ml during 2009.
continuous care through the year. These formed 78.7% of patients. Sixty-eight
per cent had viral load under 50 copies/ml and the mean viral load in this
group was 10,500 copies/ml. When the viral loads of everyone in this group
were added together, they carried only 29.5% of the total community viral load
in the clinic’s patients.
people. These formed only 6.6% of patients. However, because the mean viral
load in this group was 162,000 copies/ml, the proportion of the total viral load
carried by these patients was 37.5%. Viral loads in
undiagnosed people within the community are likely to be similar.
Between them, these two groups carried
two-thirds of the total viral load burden, so to speak, of the community. The
other third was carried by four groups who also, without exception, had higher
mean viral loads than those in continuous care.·
These are people who had been diagnosed elsewhere but had moved to Calgary.
They formed 4.8% of all patients but had a slightly higher mean viral load than those in care and were only half as likely to have viral loads under 50
copies/ml as people in care in Calgary all year.
These were people who had dropped out of care in Calgary but had then returned
some time later. Although they only formed 4.2% of people seen for care in
2009, they carried 16.6% of the total viral load burden: this was because their
mean viral load was almost as high as the newly diagnosed, at 107,000
copies/ml. Three-quarters of this group had been lost to follow-up and, of
these, over 80% said they stayed in Calgary but did not attend medical care.
are people who moved out of the area to another known clinic. These formed 2.6%
of patients and only carried 2.4% of the total viral load burden. Even so, only 43%
had viral loads under 50 copies/ml throughout the year compared with 68% in continuous care; their mean viral load
was 25,000 copies/ml.
Lost to care.
These were people who stopped attending care ('lost to follow-up'). Although they
only formed 3.1% of all patients they carried 8.5% of the total viral load
burden and their mean viral load was 73,000 copies/ml.
this means is that in total the 15% of patients who were neither in continuous
care nor newly diagnosed shared between them 33% of the total viral load of
people who attended care in 2009. Furthermore, while only 19% of those in
continuous care had viral loads over 200 copies/ml (which was regarded by the
researchers as the criterion for viral ‘suppression’), 68% of those in discontinuous
care did, and 82% of those who were either lost to follow-up (at their last
viral load test) or who returned from being lost to follow-up.