Diagnosing Rheumatoid Arthritis
C-Reactive Protein (CRP) Test
A blood test called the sedimentation rate (sed rate) is a crude measure of the inflammation of the joints. The sed rate actually measures how fast red blood cells fall to the bottom of a test tube. The sed rate is usually faster (high) during disease flares and slower (low) during remissions. Another blood test that is used to measure the degree of inflammation present in the body is the C-reactive protein. Blood testing may also reveal anemia, since anemia is common in rheumatoid arthritis, particularly because of the chronic inflammation.
The rheumatoid factor, ANA, sed rate, and C-reactive protein tests can also be abnormal in other systemic autoimmune and inflammatory conditions. Therefore, abnormalities in these blood tests alone are not sufficient for a firm diagnosis of rheumatoid arthritis.
What is C-reactive protein (CRP)?
C-reactive protein (CRP) is a blood test marker for inflammation in the body. CRP is produced in the liver and its level is measured by testing the blood.
CRP is classified as an acute phase reactant, which means that its levels will rise in response to inflammation. Other common acute phase reactants include the erythrocyte sedimentation rate (ESR) and blood platelet count.
What are the main causes of an elevated C-reactive protein (CRP)?
In general, the main causes of increased CRP and other markers of inflammation are a variety of conditions, including
Is there a link between C-reactive protein (CRP) and cardiovascular disease risk?
The elevation of CRP has also been linked to atherosclerosis and heart disease. Atherosclerosis, or cholesterol plaquing of the arteries, is known to have an inflammatory component that is thought to cause the rise in CRP levels in the blood. Atherosclerosis is also felt to be affected by age and other cardiovascular risk factors including diabetes mellitus, high cholesterol, high blood pressure, and cigarette smoking.
In atherosclerosis, the blood vessel wall becomes injured. This injury acts as focus of inflammation and leads to the formation of plaques in the blood vessel walls. The plaques typically contain blood cells of inflammation, cholesterol deposits, and debris from the injured cells in the blood vessel lining. The accumulation of these elements leads to narrowing of the wall of the blood vessel. The blood vessel narrowing can hinder the blood flow and the plaque can rupture and flake off of the blood vessel wall causing blockage and leading to strokes and heart attacks.
The burden of plaques in the body can be proportional to the degree of CRP elevation in persons with atherosclerosis. Atherosclerotic plaques can exist in different stages throughout the body.
Medically Reviewed by a Doctor on 11/11/2016