Blood tests may help predict stroke

By Anthony J. Brown, MD

NEW YORK (Reuters Health) – Testing for high blood levels
of two proteins involved in inflammation — Lp-PLA2 and CRP —
may help identify people who are at increased risk for stroke,
new research suggests.

Ultimately, measuring these proteins could help guide
preventative strategies or they may even serve as targets for
new drugs, according to the report in the Archives of Internal
Medicine.

“Predictors of stroke have received less attention than
predictors of coronary heart disease, and often it has simply
been assumed that what predicts coronary heart disease also
predicts stroke,” lead author Dr. Christie M. Ballantyne, from
Baylor College of Medicine in Houston, told Reuters Health.
“However, this is not always the case. For example, cholesterol
levels have been shown to correlate with coronary heart disease
risk, but not with stroke risk.”

Ballantyne said that measuring Lp-PLA2 and CRP levels
appears to provide information above and beyond traditional
stroke risk factors, such as high blood pressure. “For patients
who already have a high or low risk of stroke, measuring these
levels may not be particularly useful.” For patients with
intermediate risk, however, these tests may help in selecting a
preventative strategy.

The findings are based on a study of nearly 13,000
apparently healthy middle-age subjects who were followed for
about 6 years to assess the rate of stroke and other outcomes.
The study focused on 194 subjects who experienced a stroke and
766 similar subjects who did not.

Stroke patients had significantly higher levels of both
Lp-PLA2 and CRP than did comparison subjects. By contrast, and
in agreement with previous reports, LDL “bad” cholesterol
levels were similar in each group.

Further analysis showed that having high levels of either
Lp-PLA2 or CRP nearly doubled the risk of stroke. With high
levels of both, the risk of stroke was increased more than
11-fold.

Ballantyne said that his team is planning studies to see if
Lp-PLA2 and CRP-based preventative strategies can, in fact,
reduce the risk of stroke. Also, he said he is interested in
determining if these proteins are not merely markers of stroke
risk, but if they are actual mediators of the disease and thus
might serve as targets for new drug therapies.

In a related editorial, Dr. Philip Greenland and Dr.
Patrick G. O’Malley, from Northwestern University in Chicago,
agree that these tests are probably best applied to subjects
who have an intermediate stroke risk.

The editorialists comment that “given the relatively modest
incremental risk prediction capacity of both CRP and Lp-PLA2
levels beyond traditional risk factors, it would seem
inappropriate to recommend either test for routine use. As with
coronary heart disease risk assessment, new tests seem most
useful when limited to patients initially judged to be at
intermediate risk.”

SOURCE: Archives of Internal Medicine, November 28, 2005.