A common blood test can allow doctors to predict the risk of a second stroke. Researchers at the University of Virginia School of Medicine found that high levels of C-reactive protein (CRP), an enzyme found in the blood, correlates with an increased risk of ischemic stroke.

CRP is produced in the liver in response to inflammation, and is already routinely measured since it's a risk factor for coronary artery disease. The new research suggests it could be a useful tool for measuring the risk for ischemic stroke patients as well.

"The biggest risk of death for someone who has already had a stroke is to have another one," said researcher Stephen Williams, Ph.D. "So it’s really important to be able to try and target those individuals who are at the highest risk for the thing that very well may kill them."

An ischemic stroke occurs when an artery to the brain is blocked, and is most often caused by cholesterol deposits which narrow arteries in the head or neck (atherosclerosis). It's the most common type of stroke, causing 88 percent of all strokes. Each year. about 795,000 Americans have strokes, and about 185,000 of them are second strokes.

Williams and his colleagues investigated how our genes affect the levels of biomarkers such as CRP in our blood. In addition to discovering that elevated CRP levels suggest increased stroke risk, they identified gene variations that drive those risks.

"So we have the genetics influencing (CRP) levels, which then increases the risk of having a recurrent stroke. Then we went back and said alright, can we predict the increased risk purely based on the genetics, which we were able to do," Williams said.

"There's this shared genetic susceptibility not only for increased C-Reactive Protein but for increased risk for stroke," he said. "We could estimate what’s called a hazard ratio – basically the increased risk for having or not having a second stroke – based on the genetics."

Although Williams believes that in the future doctors might focus on CRP levels and a patient’s genetic makeup to determine their overall risk for a second stroke, he says that even CRP levels alone could be a useful tool in assessing risk after the initial stroke.

"Getting a CRP measure on someone is really simple," he said. "It’s just a blood draw. You don’t have to take something like a biopsy which patients might have an aversion to.

"It's not very expensive, and it’s part of routine workups that could be done for patients," he said. "However, combined with genetic information we may have even more power to identify those at greatest risk."