Should I have a CRP test?

Your risk of developing heart disease in the next 10 years is measured by your Framingham risk score and additional risk factor assessment. CRP testing is usually not necessary for healthy low-risk individuals. However, CRP can be a tiebreaker test for people with an intermediate 10-year risk (10% to 20%) when it's not clear if they need medication to control their risk factors (such as borderline high cholesterol or high blood pressure).¹

CRP is one of the numbers used in calculating your Reynolds Risk Score, a measure of 10-year heart disease risk that may be more accurate than the Framingham score in women at intermediate risk. People with heart disease or those at high-risk should ask their doctor if a CRP test is likely to change their treatment. A low CRP level does not mean that you can ignore other risk factors for heart disease.

What does the test involve?

There is no special preparation for a CRP test. A blood sample will be taken from a vein in your arm. The test takes less than a minute and you can go home immediately after.

What do the results mean?

If your CRP is high, you have a higher risk of developing heart disease. A low CRP level does not mean that you can ignore other risk factors for heart disease. A very high reading (more than 10 mg/L) indicates that you have an infection of some sort. The test should be repeated in about 2 weeks after the infection has cleared.¹

What are the risks and limitations of this test?

The CRP test is a simple blood test that carries no risks. Your CRP level can be affected by medications and other factors. hormone therapy, pregnancy, birth control pills, and intrauterine devices (IUDs) can raise CRP levels. Cholesterol lowering statin drugs, anti-inflammatories (such as aspirin, Advil, Motrin, and naproxen) may lower CRP levels. If you have chronic inflammation (such as arthritis) or have recently been ill, your CRP level will be high.

Why is CRP testing controversial?

There is an ongoing debate about how useful CRP really is. Some scientists argue that it doesn't provide any more information about your risk for heart disease than a thorough assessment of established heart disease risk factors.²¹ The early studies showing that CRP helped predict heart disease risk took some, but not all, of the established risk factors into account.

In the third National Health and Nutrition Examination Survey of more than 15,000 people 18 years and older (53% were women), only 4% of men and 10% of women had high CRP without having a borderline or abnormal heart disease risk factor.²² The risk factors that were measured included cholesterol levels, blood sugar, blood pressure, smoking, and overweight (using body mass index, BMI). Other studies have also shown no additional benefit for CRP testing.^{23, 24} It is also unclear whether knowing your CRP level will change how you are treated.

References

1. Pearson TA, Mensah GA, Alexander RW, et al. Markers of inflammation and cardiovascular disease: application to clinical and public health practice: A statement for healthcare professionals from the Centers for Disease Control and Prevention and the American Heart Association. Circulation. 2003;107:499-511.
2. Ridker PM. Clinical application of C-reactive protein for cardiovascular disease detection and prevention. Circulation. 2003;107:363-369.
3. Khera A, McGuire DK, Murphy SA, et al. Race and Gender Differences in C-Reactive Protein Levels. J Am Coll Cardiol. 2005;46:464-469.
4. Visser M, Bouter LM, McQuillan GM, Wener MH, Harris TB. Elevated C-reactive protein levels in overweight and obese adults. JAMA. 1999;282:2131-2135.
5. Albert MA, Glynn RJ, Buring J, Ridker PM. C-reactive protein levels among women of various ethnic groups living in the United States (from the Women's Health Study). Am J Cardiol. 2004;93:1238-1242.
6. Anand SS, Razak F, Yi Q, et al. C-Reactive Protein as a Screening Test for Cardiovascular Risk in a Multiethnic Population. Arterioscler Thromb Vasc Biol. 2004;24:1509-1515.
7. Best LG, Zhang Y, Lee ET, et al. C-Reactive Protein as a Predictor of Cardiovascular Risk in a Population With a High Prevalence of Diabetes: The Strong Heart Study. Circulation. 2005;112:1289-1295.
8. Blake GJ, Rifai N, Buring JE, Ridker PM. Blood Pressure, C-Reactive Protein, and Risk of Future Cardiovascular Events. Circulation. 2003;108:2993-2999.
9. Ridker PM, Buring JE, Cook NR, Rifai N. C-reactive protein, the metabolic syndrome, and risk of incident cardiovascular events: an 8-year follow-up of 14 719 initially healthy American women. Circulation. 2003;107:391-397.
10. Zebrack JS, Anderson JL, Maycock CA, et al. Usefulness of high-sensitivity C-reactive protein in predicting long-term risk of death or acute myocardial infarction in patients with unstable or stable angina pectoris or acute myocardial infarction. Am J Cardiol. 2002;89:145-149.
11. Arroyo-Espliguero R, Avanzas P, Cosin-Sales J, et al. C-reactive protein elevation and disease activity in patients with coronary artery disease. Eur Heart J. 2004;25:401-408.
12. Zouridakis E, Avanzas P, Arroyo-Espliguero R, Fredericks S, Kaski JC. Markers of Inflammation and Rapid Coronary Artery Disease Progression in Patients With Stable Angina Pectoris. Circulation. 2004;110:1747-1753.
13. Haverkate F, Thompson SG, Pyke SD, Gallimore JR, Pepys MB. Production of C-reactive protein and risk of coronary events in stable and unstable angina. European Concerted Action on Thrombosis and Disabilities Angina Pectoris Study Group. Lancet. 1997;349:462-466.
14. Morrow DA, Rifai N, Antman EM, et al. C-reactive protein is a potent predictor of mortality independently of and in combination with troponin T in acute coronary syndromes: a TIMI 11A substudy. Thrombolysis in Myocardial Infarction. J Am Coll Cardiol. 1998;31:1460-1465.
15. Lindahl B, Toss H, Siegbahn A, et al. Markers of Myocardial Damage and Inflammation in Relation to Long-Term Mortality in Unstable Coronary Artery Disease. N Engl J Med. 2000;343:1139-1147.
16. Nikfardjam M, Mullner M, Schreiber W, et al. The association between C-reactive protein on admission and mortality in patients with acute myocardial infarction. J Intern Med. 2000;247:341-345.
17. Kinjo K, Sato H, Ohnishi Y, et al. Impact of high-sensitivity C-reactive protein on predicting long-term mortality of acute myocardial infarction. Am J Cardiol. 2003;91:931-935.
18. Suleiman M, Aronson D, Reisner SA, et al. Admission C-reactive protein levels and 30-day mortality in patients with acute myocardial infarction. Am J Med. 2003;115:695-701.
19. Pai JK, Pischon T, Ma J, et al. Inflammatory Markers and the Risk of Coronary Heart Disease in Men and Women. N Engl J Med. 2004;351:2599-2610.
20. Cushman M, Arnold AM, Psaty BM, et al. C-Reactive Protein and the 10-Year Incidence of Coronary Heart Disease in Older Men and Women: The Cardiovascular Health Study. Circulation. 2005;112:25-31.
21. Lloyd-Jones DM, Liu K, Tian L, Greenland P. Narrative review: Assessment of C-reactive protein in risk prediction for cardiovascular disease. Ann Intern Med. 2006;145:35-42.
22. Miller M, Zhan M, Havas S. High Attributable Risk of Elevated C-Reactive Protein Level to Conventional Coronary Heart Disease Risk Factors: The Third National Health and Nutrition Examination Survey. Arch Intern Med. 2005;165:2063-2068.
23. Folsom AR, Chambless LE, Ballantyne CM, et al. An assessment of incremental coronary risk prediction using C-reactive protein and other novel risk markers: the atherosclerosis risk in communities study. Arch Intern Med. 2006;166:1368-1373.
24. Wilson PW, Nam BH, Pencina M, et al. C-reactive protein and risk of cardiovascular disease in men and women from the Framingham Heart Study. Arch Intern Med. 2005;165:2473-2478.
25. Nissen SE, Tuzcu EM, Schoenhagen P, et al. Effect of Intensive Compared With Moderate Lipid-Lowering Therapy on Progression of Coronary Atherosclerosis: A Randomized Controlled Trial. JAMA. 2004;291:1071-1080.
26. Nissen SE, Tuzcu EM, Schoenhagen P, et al. Statin Therapy, LDL Cholesterol, C-Reactive Protein, and Coronary Artery Disease. N Engl J Med. 2005;352:29-38.
27. Ridker PM, Cannon CP, Morrow D, et al. C-Reactive Protein Levels and Outcomes after Statin Therapy. N Engl J Med. 2005;352:20-28.
28. Ridker PM, Rifai N, Pfeffer MA, Sacks F, Braunwald E. Long-Term Effects of Pravastatin on Plasma Concentration of C-reactive Protein. Circulation. 1999;100:230-235.
29. Albert MA, Danielson E, Rifai N, Ridker PM, for the PRINCE Investigators. Effect of Statin Therapy on C-Reactive Protein Levels: The Pravastatin Inflammation/CRP Evaluation (PRINCE): A Randomized Trial and Cohort Study. JAMA. 2001;286:64-70.
30. Ridker PM, Cushman M, Stampfer MJ, Tracy RP, Hennekens CH. Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men. N Engl J Med. 1997;336:973-979.
31. Gaspardone A, Crea F, Versaci F, et al. Predictive value of C-reactive protein after successful coronary-artery stenting in patients with stable angina. Am J Cardiol. 1998;82:515-518.
32. Okita K, Nishijima H, Murakami T, et al. Can exercise training with weight loss lower serum C-reactive protein levels? Arterioscler Thromb Vasc Biol. 2004;24:1868-1873.
33. Church TS, Barlow CE, Earnest CP, et al. Associations Between Cardiorespiratory Fitness and C-Reactive Protein in Men. Arterioscler Thromb Vasc Biol. 2002;22:1869-1876.
34. Esposito K, Pontillo A, Di Palo C, et al. Effect of Weight Loss and Lifestyle Changes on Vascular Inflammatory Markers in Obese Women: A Randomized Trial. JAMA. 2003;289:1799-1804.
35. Albert MA, Glynn RJ, Ridker PM. Alcohol Consumption and Plasma Concentration of C-Reactive Protein. Circulation. 2003;107:443-447.
36. Chrysohoou C, Panagiotakos DB, Pitsavos C, Das UN, Stefanadis C. Adherence to the Mediterranean diet attenuates inflammation and coagulation process in healthy adults: The ATTICA Study. J Am Coll Cardiol. 2004;44:152-158.
37. Esposito K, Marfella R, Ciotola M, et al. Effect of a mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome: a randomized trial. JAMA. 2004;292:1440-1446.