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VACS Index score can help identify HIV-positive patients most at risk of neurocognitive decline
Michael Carter, 2016-07-04 07:00:00
A combination of
simple, routine blood tests may be able to predict which HIV-positive patients
are especially vulnerable to neurocognitive decline, according to US research
published in Clinical Infectious Diseases. Patients with high VACS Index scores had an
increased risk of experiencing a decline in neurocognitive function and were
also significantly more likely to develop new neurocognitive problems.
“Changes in VACS
Index correspond to changes in neurocognitive function over time in a large,
well-characterized HIV-infected cohort,” write the authors.
advances in treatment and care, neurocognitive impairment (NCI) remains common
in patients with HIV, occurring in between 30% and 50% of individuals. In most
patients this is mild. Nevertheless, even milder forms of impairment can have a
negative impact on day-to-day life.
It is therefore
important to identify patients which patients are at risk of developing
neurocognitive impairment and also those with baseline impairment at high risk
of further decline.
The Veterans Aging
Cohort (VACS) Index was developed as a marker of disease severity in
HIV-positive patients. It is based on the results of blood tests that are
performed as part of routine care, such as CD4 count, viral load, renal and liver
function, anaemia and hepatitis C screening. A higher VACS Index score has
consistently been associated with an increased risk of death in patients,
hospitalization and also diseases usually associated with older age, such as
frailty, fragility fracture and low muscle strength.
wanted to see if VACS Index score could predict neurocognitive change and
incident neurocognitive impairment.
designed a study involving 655 HIV-positive adults receiving care at the
University of California, San Diego. Patients were followed for up to six
The association between
baseline VACS Index score and subsequent neurocognitive change.
Whether changes in VACS index
scores over time were correlated with changes in neurocognitive function.
Whether VACS Index scores
predicted time to incident neurocognitive impairment in patients with normal
neurocognitive function at baseline.
major psychiatric disorders or brain injury were excluded from recruitment.
function was assessed using a comprehensive battery of tests. Initial scores
were converted in T scores adjusted for age, education, sex and race. The
adjusted T scores were then averaged to obtain global and domain T scores.
Participants had a
mean age of 43 years, 83% were male, 60% were white, mean CD4 count was 346
cells/mm3, 67% had an AIDS diagnosis, 61% were taking antiretroviral
therapy and 51% had an undetectable viral load. Three-quarters reported a
history of substance abuse.
At baseline, 40%
were assessed as having neurocognitive impairment. Median VACS Index score was
22. Patients with and without neurocognitive impairment were broadly
There was no
significant association between baseline VACS Index score and neurocognitive
However, there was
a significant association between higher VACS Index and worse global and domain
neurocognitive performance, even after adjusting for potential confounders (p
Higher VACS Index
was associated with poorer memory scores in patients not taking antiretrovirals
(p < 0.01) but not for patients taking HIV therapy.
Analysis of the
60% of patients with no neurocognitive impairment at baseline showed that
higher baseline VACS Index scores were associated with increased chances of
developing impairment (p < 0.01). After controlling for factors such as
nadir CD4 count and baseline depression this association ceased to be
significant. But in the time-dependent analyses, higher VACS Index scores were
associated with a significantly increased risk of incident neurocognitive
impairment (HR, 1.17; 95% CI, 1.06-1.29, p < 0.01).
higher VACS Index scores were significantly more likely to develop
neurocognitive impairment compared to patient with low (p < 0.01) and
moderate (p < 0.01) VACS Index scores. Moreover, patients with higher VACS
Index scores were also significantly more likely than other patients to
experience neurocognitive decline (p = 0.02).
VACS Index scores may not be a good predictor of neurocognitive change in the
longer term. Changes in VACS Index scores, however, correspond to changes in
neurocognition,” conclude the authors. “Having very high VACS Index scores
might indicate a notable increased risk of neurocognitive decline and incident
NCI. These findings support the VACS Index as a simple tool for identifying
HIV-infected patients who are at high risk of NCI and might warrant further