Despite major progress in the last 30 years, heart disease continues to be a major health problem. It is the leading cause of death in the United States alone. And overall, about one-third of people who have heart attacks die. Roughly 1.5 million Americans suffer a heart attack each year. That’s one heart attack every 20 seconds. And firefighters are no exception. Since 1990, the number of firefighter sudden-cardiac deaths each year has fluctuated between 40 and 50.

Fire departments today are becoming more aware of these problems and many have developed wellness and fitness initiatives to help fight off cardiovascular disease and promote a healthier lifestyle. However, fire departments today may not be aware that an inexpensive and easy test of C-reactive protein, or CRP, could detect early warning signs of cardiovascular disease, even when all other cardiovascular profile markers are normal.

This article will examine the following whether 
CRP is an effective predictor of heart disease and how CRP testing compares to other heart-disease tests. Should CRP testing prove to be viable and fiscally responsible, then employing its use as another marker to head off coronary artery disease (CAD) would help save firefighters from future sudden cardiac death and cardiovascular related maladies.

What is CRP?

C-reactive protein (CRP) is produced by the liver in response to inflammation in the body. It normally is not found in the blood stream in high amounts. However, when an injury, infection, or inflammatory process occurs, CRP is rapidly produced. It is measured in milligrams per liter of blood. A reading of >10 mg/L would indicate a systemic inflammation process, such as a bacterial or viral infection (following surgery, for instance), or patients with chronic inflammatory diseases such as rheumatoid arthritis. The amount of CRP produced by the body varies from person to person, and this is affected by their genetic makeup and their lifestyle.

With advances in technology, more-precise measurements of CRP now can be achieved. This test is called the high-sensitivity C-reactive protein (hs-CRP) test. Its measurements range from 0.1 to 3.0 mg/L; the wider range provides more-precise measurements that are useful in identifying the inflammation process associated with coronary artery disease.

C-reactive protein is one of the acute-phase proteins that increase when inflammation occurs in the body. It has been suggested by many researchers that testing for hs-CRP levels may be a new way to assess cardiovascular disease risk. Three years ago, the Centers for Disease Control and Prevention and the American Heart Association released a joint statement about using inflammatory markers in clinical and public-health practices.

This statement came about after a review of evidence that associated CRP with coronary heart disease and stroke.
High levels of hs-CRP consistently predict new coronary events in patients with unstable angina and acute myocardial infarctions. In addition, higher levels of hs-CRP are associated with lower survival rates. Even after adjusting for other prognostic factors, hs-CRP was still useful as a predictor of heart attack, the AHA said.

In calculating an individual’s 10-year risk profile for heart attack, traditional risk factors are incorporated into a test. The typical variables are age, cholesterol levels, high blood pressure, smoking status, and diabetes. One approach, the Framingham model, utilizes these variables to perform a risk analysis. This approach, based on a long-term heart study, has been used for nearly a decade to evaluate the 10-year risk of heart attacks in men and women.

In a recent trial that used the Framingham model, women were given a percentage score to evaluate their risk of heart disease. If they had a score of less than 5%, their risk was considered “low.” A score ranging from 5% to 10% indicated a “low to moderate” risk. A score between10% and 20% was considered “moderate to high.” Anything over 20% was considered “high.” Some of the moderate-to-high women, and all of the women who fell into the “high” range, were advised to modify their diets and other lifestyle factors, and to possibly use pharmacological means to lower their levels of LDL cholesterol.

Interestingly, the researchers found that up to 20% of heart attacks in women occur without any of the Framingham risk factors. They have reasoned that this is the result of an absence of inflammatory markers or genetic predisposition. A woman who is at a moderate risk level, as defined by the Framingham criteria, but who has an elevated hs-CRP level could be at a high risk even if her cholesterol levels are within normal parameters.

Dr. Paul Ridker, director of the Center for Cardiovascular Disease Prevention, working with researchers from Boston’s Brigham and Women’s Hospital — which is affiliated with Harvard University’s medical center — set out to establish a different test using additional markers, including hs-CRP and family history. A test was administered to 24,558 women age 45 and older. A total of 35 risk factors were assessed, and the women were followed over a 10-year period. They were monitored for heart attacks, stroke, bypass surgery, and death.

Two-thirds of the women were selected at random in order to develop a risk model that better takes into account inflammatory markers and heredity. This new model is based on eight risk factors: the original five from the Framingham model plus hs-CRP, parental history of a heart attack before the age of 60, and the presence of hemoglobin A in women with diabetes.

The researchers applied this new model to the remaining one-third of women in the study group and found it to be more accurate than the Framingham model. Of the participants who initially had moderate risk scores, nearly half of them were reclassified into higher or lower risk groups that better matched their profiles for cardiovascular events. This newer model for testing is called the “Reynolds Risk Score.”

Inflammation & Heart Disease

A growing body of research has shown a link between some inflammatory processes and heart disease. One such link shows a higher risk of developing coronary artery disease for those who have pericoronitis (infection around the third molar), gingivitis, and infections around the teeth, or a tooth that has decayed and the tip of the root remains.

According to the AHA, oral infections are thought to produce inflammation that might be associated with CAD. All pathologies that might generate inflammation were examined, and pericoronitis was the strongest predictor.

Some scientists at Columbia University in New York City reported that older adults with higher-than-normal amounts of gum disease tend to have thicker carotid arteries, suggesting a link between cardiovascular disease and gum inflammation. Their belief is that if gum disease bacteria causes thickening of the arteries, it’s possible that it might be because organisms are stimulating the immune system, which in turn causes inflammation that results in clogging of the arteries.

In one study involving the United States, Canada, Great Britain, Sweden and Germany, researchers found that people with advanced gum disease were at 25% to 100% more likely to suffer a heart attack than those without such disease. They also believe that once the bacteria is in the blood stream, it can trigger the formation of blood clots and that inflammation may represent another mechanism for the formation of clots.

Another link suggesting that inflammation plays a vital role in cardiovascular disease involves diabetes. Studies from the Joslin Diabetes Center show a two-to threefold increase in heart disease in patients with diabetes compared with those without diabetes. There are numerous mechanisms involved; one such mechanism involves an increased level of low-grade inflammation in the arterial lining, a process that leads to blood-vessel changes that lead to heart disease.

Pros & Cons of CRP Testing

Testing for hs-CRP involves a simple, low-cost blood test that can be initiated before or after eating. No fasting is required and no other preparations are necessary. Each test requires approximately 5 milliliters of blood that is extracted from a vein in the arm. The whole procedure takes just a few minutes.

Some people will experience a mild stinging or burning sensation during the blood draw, with minor swelling or bruising in some cases. However, no side effects associated with the test, and any problems are a result of the needle insertion that occurs during the blood draw. Blood taken during physicals for normal lab tests can be used to test for hs-CRP.

One hundred percent of the doctors queried during a telephone survey conducted for this article agreed that hs-CRP is beneficial as an additional marker for heart disease. However, some disagreed that it was a better predictor of heart disease. Most felt that it was beneficial when used in combination with other heart tests. But one doctor did not think that hs-CRP was a good predictor of heart disease.

Most of the doctors agreed that using hs-CRP testing during physical-fitness testing would help to predict firefighter cardiac events. One doctor did not agree. However, all of the physicians felt that hs-CRP testing should be conducted in addition to cholesterol testing and most thought that it should be used routinely during physical-fitness lab tests.

According to Dr. Wayne Peate, the Tucson Fire Department has been using hs-CRP testing for the past four years. He said that 10 firefighters were found to have elevated hs-CRP levels that required changes in their lifestyles.

A wellness-and-fitness company that conducts physicals for approximately 20 fire departments in California was surveyed. About 25% of those fire departments incorporate hs-CRP testing into their physical-fitness testing. The company went on to say that budget constraints usually were the reason for not conducting the hs-CRP testing.

Conclusion

Cardiovascular disease is a major killer worldwide and can strike even when cholesterol, blood pressure, and other markers are normal. Research suggests that when hs-CRP and genetic profiles are added to the normal cardiac markers, some people who normally would be categorized as being moderate risks for heart disease are put into a higher risk group due to low-grade inflammation.

Low-grade inflammation now is being linked to increased risks of cardiovascular disease in many different etiologies, including diabetes and periodontal disease. One way to measure this inflammation is by using hs-CRP testing. It is an easy test to perform and all that is required is a simple blood draw and no fasting is required. It is also inexpensive.

Consequently, fire departments need to become more aware of hs-CRP testing and include it in their yearly budgets. This will ensure that every possible risk factor for coronary artery disease is detected early.

William D. Bathe is a captain with the Tucson (Ariz.) Fire Department, and currently is assigned to Battalion 1 as an EMS captain. He has been a captain for more than eight years and a medic for more than 12 years. Prior to his career in the fire service, he was a professional baseball player for 12 years, playing three years in the major leagues for the San Francisco Giants and Oakland Athletics.

Related Stories

• Better Health is Within Reach
• A Silent Killer Strikes the Fireground
• Personal Trainer