C-Reactive Protein (CRP)

BY DR. D. P. Atukorale

FOLLOWING the publication of an article in a Sunday journal, there are some misconceptions in the minds of the readers that the test called C-Reactive Protein (CRP) is specific for diagnosis of heart attacks and strokes.

CRP is a test that measures the concentration of a protein in serum that indicates acute inflammation. Inflammation by the way is a defensive reaction of the body's tissues to invasion by pathogenic micro-organism such as bacteria and viruses or in the presence of foreign body or any other injury.

CRP is a special type of protein produced by the liver that is present during episodes of acute inflammation. While CRP is not a specific test for heart disease and stroke, it gives a general indication of acute inflammation in the body.

Normally there is no CRP in the blood serum of normal healthy people although there may be very low levels of High Sensitive CRP (hsCRP) in normal people. Abnormal levels of CRP occur in a number of diseases such as:

(a) Rheumatoid Arthritis

(b) Rheumatic Fever

(c) Cancer e.g. colorectal cancer

(d) Tuberculosis (TB)

(e) Pneumococcal Pneumonia

(f) Myocardial Infarction (heart attacks)

(g) Strokes (brain attacks)

(h) Systemic Lupus Eryhtematosis (SLE)

(i) Peripheral Vascular Disease (e.g. intermittent claudication)

(j) Certain normal people who may develop hypertension later

(k) During last half of pregnancy

(l) With the use of contraceptives

CRP, head disease and strokes

As mentioned earlier, inflammation is the process by which body responds to injury. In atherosclerosis (process by which fatty deposits build up in the inner lining of arteries) there is believed to be low grade inflammation and the possible infective bacteria include Chlamydia pneumonia, Helicobacter pylori and viruses such as herpes simplex virus and cytomegalovirus.

It has been suggested that testing CRP in the blood may be a new way to assess risk for cardiovascular diseases such as heart disease and strokes; but as mentioned earlier, it is not a specific test for heart attacks and strokes.

A large number of research studies done in the recent past show that CRP can predict cardiovascular events in people who have high levels of CRP or hsCRP. Patients with unstable angina (severe angina) and acute myocardial infarction with high serum levels of CRP have a low survival rate.

CRP and angioplasty results

Recent research studies show that high levels of CRP in heart patients who have undergone angioplasty (PTCA) mean that the artery may have closed after it has been opened by balloon angioplasty. So cardiologists should perform this simple test before and after PTCA to assess the success of their procedure.

CRP and strokes and peripheral vascular disease

High levels of CRP appear to predict prognosis (prospect of recovery) and recurrent events in patients with strokes and peripheral vascular disease (intermittent claudication). The true independent association between CRP and cardiovascular events has not yet been established.

Normal range of high sensitive CRP

If the hsCRP is lower than 1mg/per litre, a person has a low risk of developing a heart attack or a stroke. If hsCRP level is between 1 and 3 mg per litre, a person has an average risk of developing a heart attack or a stroke.

So if a patient has an unusually high serum level of hsCRP, that person should undergo a check-up to exclude risk factors for cardiovascular disease.

If a person with high CRP has no risk of Coronary Heart Disease or strokes such as hypertension, hyperlipidaemia, smoking and diabetes, the physician should exclude other diseases such as arthritis, TB, cancer or SLE.

Estimation or CRP in patients on statin therapy

Majority of physicians prescribe statins such as lovastatins, simvastatin and atorvastatin to patients with elevated LDL (bad) cholesterol when they find it difficult to control the cholesterol levels by low saturated and low cholesterol diet and exercise. Side effects of statin-therapy are rare.

During the last 25 years of my experience I have come across a very few patients (less than 10) who developed serious side effects out of thousands of patients I have treated with statins. Once statins were withdrawn, the side effects subsided, in all the patients.

Statins are a group of wonder drugs and there is scientific evidence to show that those on statins have a low incidence of cancer and other chronic diseases.

Use of statins for heart attacks

It is common practice among majority of cardiologists to prescribe statins especially atorvastatin to all patients suffering from unstable angina (severe angina, acute coronary syndrome) and acute myocardial infarction on admission of the patients to intensive care unit (ICU or CCU) irrespective of the fact that these patients have high blood cholesterol or not, as it has been found that statins have a beneficial effect on the prognosis of these patients because statins have a beneficial effect on the endothelial function.

There is scientific evidence to show that use of statins results in decrease in the level of CRP in these patients with unstable angina and major heart attacks. Other very useful blood test done in patients with acute coronary syndrome and heart attacks is Troponin T or Tropoin I.

If the CRP levels are low and if Troponin T or Troponin I are repeatedly negative, such patients can be observed in an intermediate coronary care unit or in a medical ward even if ECG is abnormal. If CRP or hsCRP is high, the test should be repeated after statin therapy with a view to assess the prognosis of these heart patients.

CRP and hypertension

Recent research suggests that people with elevated hsCRP levels are at a higher risk of developing hypertension and this suggests that hypertension is an inflammatory disease (Howard et al, JAMA, 2003, 290, 2945-2967). Howard et al say that people with elevated hsCRP levels are at a higher risk of development of hypertension.

High CRP levels and coronary risk factors

Recent research suggests that elevated CRP levels are also found in people with other coronary risk factors such as smoking obesity and lack of exercise, whereas athletic individuals tend to have lower levels of hsCRP levels.

Thus there appears to be an association between CRP level of person and future development of heart disease.

This is true even in normal healthy people with normal blood cholesterol levels. Therefore all physicians should include this very useful blood test (hsCRP) in the assessment of the cardiovascular risk of their patients.

At present, both CRP and high sensitive CRP (hsCRP) can be performed in a number of recognised private labs. I understand that it costs Rs. 550 for estimation of hsCRP in the private sector in Colombo.

As far as I am aware there are no facilities to carry out above test in the Sri Lankan government hospitals at present.