Researchers have developed a blood test that may help detect heart disease in asymptomatic individuals by measuring the immune system’s response to inflammation, a symptom tied to various age-related diseases like dementia and arthritis. In a nine-year-long study of 90 people without heart disease, the test, which spits out a number indicating risk, was better at predicting the condition than a CRP test or cholesterol testing, which is accurate only about half the time.
Heart disease remains the leading cause of death worldwide, accounting for about 610,000- or one in four- deaths each year in the United States alone, according to the Centers for Disease Control and Prevention.
“So these are fields that need to talk to each other more [so that] cardiologists can feel comfortable looking at immunological data and deciding what might work best for their patients.” Davis and his team began by administering an annual flu shot to 29 people – 19 older and 10 younger – to study how their cells responded to the vaccine.
Over the course of nine years, this participant group would expand to 90 people- 60 people over age 60 and 30 people under age 40- all of who were given the vaccine and assessed annually with various tests to study their immune function and markers of inflammation. It’s well known that as individual ages, his or her immune system falters. That’s why older patients don’t respond as well to the flu vaccine as younger people. The immune system consists of specialized white blood cells, which fight infection and talk to each other with small, secreted molecules called cytokines, said Davis, who is also a microbiology and immunology professor at Stanford.
Cytokines are known to kick the immune system into high gear and are essentially the hormones of the immune system, while the blood is the highway of the immune system. Separately in a lab dish, Davis, and his team analyzed how participants’ immune cells responded to cytokine stimulation. In the older patients, pre-stimulation levels of STAT protein activation were significantly higher than in those from young people, suggesting their immune systems are constantly in an overstimulated state.
“So they have a low level of cytokines in blood that is chronically stimulating white blood cells- that would be chronic inflammation, and it doesn’t suggest good things about how well your immune system might be functioning.” Using those observations and mixing 15 cytokine-responsive measurements, researchers devised a cytokine response score.
Higher scores signaled lower inflammation and greater immune response. Researchers gathered the cytokine response scores of 40 older subjects and cross-referenced results from their cardiovascular health assessments, which they took up to two years later.
“And of course people are not always healthy, and in a long-range study they die of different things-cardiovascular disease and cancer-and ‘Can we see anything leading up to that that could be a signal of someone that’s in danger?'” As for the cytokine response score, the test is too complex to be rolled out in a clinical setting just yet, but Davis said it could be easily simplified and commercialized.