Question

I've read a lot about the use of the CRP as a test for heart trouble. Just how necessary is such a test? Not all labs seem to do it, and I've heard it's expensive.

Answer

C-reactive protein (CRP) is a substance found in the blood that's a 'marker' for the presence of inflammation somewhere in the body. The value is normally less than 3 mg/L.
 

In recent years the role of inflammation in causing coronary heart disease has been recognized, and some specialists think that it's the main cause. However, there are obviously other causes, so that differing specialists claim that CRP is an irrelevant test.
 

A study¹ has just been reported that tries to pinpoint the relevance of the CRP test for predicting coronary heart disease events (i.e. a heart attack or myocardial infarction (MI), and unstable or persistent angina). Baltimore scientists looked at the CRP levels, total cholesterol, low-density lipoprotein cholesterol, triglycerides, fasting blood glucose, blood pressure, and body mass index (BMI) in over 15,000 individuals. They found that high CRP levels were significantly more common in people who were obese, overweight, or had diabetes. Moreover, they were rarely raised in people who didn't have any borderline or raised result for the other risk factors measured. Overall, the chances of a raised CRP level being due to the presence of an abnormal or borderline coronary heart disease risk factor was about 70%.
 

All this suggests that CRP assays are, in large measure, due to 'traditional' coronary heart disease risk factors. So if your doctor is checking your blood lipid levels, your fasting blood sugar, your blood pressure, and your weight, you really won't benefit much from a CRP assay.
 

Footnotes
1. High attributable risk of elevated C-reactive protein level to conventional coronary heart disease risk factors. M. Miller, M. Zahn, S. Havas, Arch Intern Med, 2005, vol. 165, pp. 2063--2068

Related Links
MedlinePlus: C-Reactive Protein