Viral load in HIV infection cannot predict individual's CD4 cell count decline
The use of baseline viral load measurements to drive decisions about when to start antiretroviral therapy for untreated HIV-infected individuals has been called into question by research published this week in JAMA (2006;296:1498).
Researchers suggest that the viral load of an untreated individual appears
to have little value in predicting their rate of CD4 cell count decrease.
The researchers analysed data from two cohorts of HIV-infected persons
(n=1,289 and n=1,512) and calculated how much of the person-to-person
variation in rate of CD4 cell loss could be accounted for on the basis
of each person’s initial viral load. They found that it explained
only about 5 per cent of the variation.
“These findings represent a major departure from the notion that
plasma HIV RNA level is a reliable predictor of rate of CD4 cell loss
in HIV
infection and challenge the concept that the magnitude of viral replication
(at least as reflected by plasma levels) is the main determinant of the
speed of CD4 cell loss at the individual level,” the researchers
say.
“The clinical implications are that in the majority of cases, an
individual patient’s plasma HIV RNA level at the time of presentation
for clinical care cannot predict, to a significant extent, the rate of
CD4
cell decline that he or she will experience over the subsequent years
and is therefore of limited clinical value in shaping the decision to
initiate antiretroviral therapy,” they conclude.
The authors of an accompanying editorial suggest that a better understanding
of the as yet unknown factors that drive CD4 depletion will lead to improvements
in the treatment of HIV infection.
“A better understanding of the immunogenic and genetic factors
that drive HIV-associated CD4 cell loss may translate to novel therapeutic
approaches
that could favourably shift the pathogen-host balance,” they write
(ibid, p1523). |
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