C-reactive protein (CRP) is one of the circulating blood proteins that help the host defense system begin immune defense by phagocytosis performed by macrophage. Its opsonization of target cells is much less precise than from immunoglobulin generated by B-lympocytes for T8 lymphocytes. When activated, it binds, with the antigen, to a surface receptor on macrophages and opsonize the threatening cells.
Along with the erythrocyte sedimentation rate, an elevated c-reactive protein suggests that an acute inflammatory disorder exists. The c-reactive protein may be a more accurate predictor inflammatory disease than the erythrocyte sedimentation rate
Predicting risk of atherosclerosis
Abnormal high sensitivity CRP values may assist in assessing lipid measurements in apparently healthy people due to the theory that chronic inflammation precedes atherosclerosis. However, a review found that the ability of the CRP to add to other methods of predicting coronary heart disease such as the Framingham risk tool is limited except in one study (AUC increased from 0.735 to 0.750). In one study, the CRP did not add to the coronary calcium score.
Studies that report benefit use the natural logarithm transformation of the CRP and measure the net reclassification rate rather than the c-index. Most, but not all, recent studies have transformed the CPR levels prior to analysis. First, an analysis of Framingham data showed small improvement from using the log of the CRP (AUC increased from 0.795 to 0.799 and 12% of patients had improved estimates - net reclassification improvement (NRI) = 11%). Second, the hsCRP added similarly to the predictions in the Women's Health Study. Third, the transformed hsCRP improved the classifiation of Swedish subjects, if the subjects had intermediate-risk (10-year predicted risk, 6% to <20%). Fourth, a Scottish cohort found that the transformed CRP did not add much to the prediction of coronary heart disease, but this cohort only reported the c-index. However, the transformed hsCRP is not always a significant predictor.
The natural logarithm transformation of the CRP is part of the Reynolds score which has been proposed as an improvement to the Framingham risk for the prediction of coronary heart disease (AUC increased from 0.689 to 0.700 in men and from 0.805 to 0.808 in women). The Reynolds score has been validated in the Women's Genome Health Study. An online calculator is at http://www.reynoldsriskscore.org/.
Risk factor modification, particularly the use of aspirin and the hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins), may reduce plaque inflammation. Statin therapy benefited about 1 of every 170 patients with LDL cholesterol less than 130 mg per deciliter (3.4 mmol per liter), Framingham risk score of 10%, and high-sensitivity C-reactive protein levels of 2.0 mg per liter or higher who took rosuvastatin 20 mg daily for 2 years if they are similar to the patients in the JUPITER randomized controlled trial (number needed to treat for two years is 170). The frequency of death from any cause fell from 2.8% to 2.2% (number needed to treat for two years is 180). However, this trial was stopped early after an interim analysis so it is likely that the results are exaggerated.
Predicting reduction in heart disease from therapy with statins
In patients without previous heart disease, LDL cholesterol less than 130 mg per deciliter (3.4 mmol per liter), and high-sensitivity C-reactive protein levels of 2.0 mg per liter or higher, hydroxymethylglutaryl-coenzyme A reductase inhibitor (statin) therapy benefited about 1 of every 170 patients who took rosuvastatin 20 mg daily for 2 years in the JUPITER randomized controlled trial (number needed to treat for two years is 170). The frequency of death from any cause fell from 2.8% to 2.2% (number needed to treat for two years is 180). However, this trial was stopped early after an interim analysis so it is likely that the result is exaggerated.
However, the Heart Protection Study found benefit from primary prevention for patients with and without a high CRP who received simvastatin over 5 years.
Lowering the C-reactive protein
Obesity and unhealthy diet may raise CRP.
Both aspirin and statins (lovastatin and rosuvastatin) can lower the C-reactive protein with a synergistic effect from combining both drugs. Aspirin is especially effect in reducing coronary heart disease among people with eleveate C-reactive proteins.
- Husain TM, Kim DH (Spring 2002), "C-Reactive Protein and Erythrocyte Sedimentation Rate in Orthopaedics", University of Pennsylvania Orthopedic Journal 15: 13-16
- Colombet I, Pouchot J, Kronz V, Hanras X, Capron L, Durieux P et al. (2010). "Agreement between erythrocyte sedimentation rate and C-reactive protein in hospital practice.". Am J Med 123 (9): 863.e7-13. DOI:10.1016/j.amjmed.2010.04.021. PMID 20800157. Research Blogging.
- Cals JW, Butler CC, Hopstaken RM, Hood K, Dinant GJ (2009). "Effect of point of care testing for C reactive protein and training in communication skills on antibiotic use in lower respiratory tract infections: cluster randomised trial". BMJ 338: b1374. PMID 19416992. PMC 2677640.
- Zacho J, Tybjaerg-Hansen A, Jensen JS, Grande P, Sillesen H, Nordestgaard BG (October 2008). "Genetically elevated C-reactive protein and ischemic vascular disease". N. Engl. J. Med. 359 (18): 1897–908. DOI:10.1056/NEJMoa0707402. PMID 18971492. Research Blogging.
- Elliott, Paul; John C. Chambers, Weihua Zhang, Robert Clarke, Jemma C. Hopewell, John F. Peden, Jeanette Erdmann, Peter Braund, James C. Engert, Derrick Bennett, Lachlan Coin, Deborah Ashby, Ioanna Tzoulaki, Ian J. Brown, Shahrul Mt-Isa, Mark I. McCarthy, Leena Peltonen, Nelson B. Freimer, Martin Farrall, Aimo Ruokonen, Anders Hamsten, Noha Lim, Philippe Froguel, Dawn M. Waterworth, Peter Vollenweider, Gerard Waeber, Marjo-Riitta Jarvelin, Vincent Mooser, James Scott, Alistair S. Hall, Heribert Schunkert, Sonia S. Anand, Rory Collins, Nilesh J. Samani, Hugh Watkins, Jaspal S. Kooner (2009-07-01). "Genetic Loci Associated With C-Reactive Protein Levels and Risk of Coronary Heart Disease". JAMA 302 (1): 37-48. DOI:10.1001/jama.2009.954. Retrieved on 2009-07-06. Research Blogging.
- 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 Jul 4;145(1):35-42. PMID 16818927
- Koenig W, Löwel H, Baumert J, Meisinger C (March 2004). "C-reactive protein modulates risk prediction based on the Framingham Score: implications for future risk assessment: results from a large cohort study in southern Germany". Circulation 109 (11): 1349–53. DOI:10.1161/01.CIR.0000120707.98922.E3. PMID 15023871. Research Blogging.
- Detrano R, Guerci AD, Carr JJ, et al (March 2008). "Coronary calcium as a predictor of coronary events in four racial or ethnic groups". N. Engl. J. Med. 358 (13): 1336–45. DOI:10.1056/NEJMoa072100. PMID 18367736. Research Blogging.
- de Ruijter W, Westendorp RG, Assendelft WJ, et al (2009). "Use of Framingham risk score and new biomarkers to predict cardiovascular mortality in older people: population based observational cohort study". BMJ 338: a3083. PMID 19131384. PMC 2615548.
- Wang TJ, Gona P, Larson MG, et al (December 2006). "Multiple biomarkers for the prediction of first major cardiovascular events and death". N. Engl. J. Med. 355 (25): 2631–9. DOI:10.1056/NEJMoa055373. PMID 17182988. Research Blogging.
- Wilson PW, Pencina M, Jacques P, Selhub J, D'Agostino R, O'Donnell CJ (2008). "C-reactive protein and reclassification of cardiovascular risk in the Framingham Heart Study.". Circ Cardiovasc Qual Outcomes 1 (2): 92-7. DOI:10.1161/CIRCOUTCOMES.108.831198. PMID 20031795. PMC PMC3033831. Research Blogging.
- Cook NR, Buring JE, Ridker PM (July 2006). "The effect of including C-reactive protein in cardiovascular risk prediction models for women". Ann. Intern. Med. 145 (1): 21–9. PMID 16818925.
- Melander, Olle; Christopher Newton-Cheh, Peter Almgren, Bo Hedblad, Goran Berglund, Gunnar Engstrom, Margaretha Persson, J. Gustav Smith, Martin Magnusson, Anders Christensson, Joachim Struck, Nils G. Morgenthaler, Andreas Bergmann, Michael J. Pencina, Thomas J. Wang (2009-07-01). "Novel and Conventional Biomarkers for Prediction of Incident Cardiovascular Events in the Community". JAMA 302 (1): 49-57. DOI:10.1001/jama.2009.943. Retrieved on 2009-07-06. Research Blogging.
- Hamer M, Chida Y, Stamatakis E (August 2009). "Utility of C-reactive protein for cardiovascular risk stratification across three age groups in subjects without existing cardiovascular diseases". Am. J. Cardiol. 104 (4): 538–42. DOI:10.1016/j.amjcard.2009.04.020. PMID 19660608. Research Blogging.
- Kavousi M, Elias-Smale S, Rutten JH, Leening MJ, Vliegenthart R, Verwoert GC et al. (2012). "Evaluation of newer risk markers for coronary heart disease risk classification: a cohort study.". Ann Intern Med 156 (6): 438-44. DOI:10.1059/0003-4819-156-6-201203200-00006. PMID 22431676. Research Blogging.
- Ridker PM, Paynter NP, Rifai N, Gaziano JM, Cook NR (November 2008). "C-reactive protein and parental history improve global cardiovascular risk prediction: the Reynolds Risk Score for men". Circulation 118 (22): 2243–51, 4p following 2251. DOI:10.1161/CIRCULATIONAHA.108.814251. PMID 18997194. Research Blogging.
- Ridker PM, Buring JE, Rifai N, Cook NR (February 2007). "Development and validation of improved algorithms for the assessment of global cardiovascular risk in women: the Reynolds Risk Score". JAMA 297 (6): 611–9. DOI:10.1001/jama.297.6.611. PMID 17299196. Research Blogging.
- Paynter NP, Chasman DI, Buring JE, Shiffman D, Cook NR, Ridker PM (January 2009). "Cardiovascular disease risk prediction with and without knowledge of genetic variation at chromosome 9p21.3". Ann. Intern. Med. 150 (2): 65–72. PMID 19153409.
- F Brian Boudi, Chowdhury H Ahsan, James L Orford, Andrew P Selwyn (Aug 10, 2006), "Atherosclerosis", eMedicine
- Ridker PM, Danielson E, Fonseca FA, et al (November 2008). "Rosuvastatin to Prevent Vascular Events in Men and Women with Elevated C-Reactive Protein". N. Engl. J. Med.. DOI:10.1056/NEJMoa0807646. PMID 18997196. Research Blogging.
- Ridker PM (November 2003). "Rosuvastatin in the primary prevention of cardiovascular disease among patients with low levels of low-density lipoprotein cholesterol and elevated high-sensitivity C-reactive protein: rationale and design of the JUPITER trial". Circulation 108 (19): 2292–7. DOI:10.1161/01.CIR.0000100688.17280.E6. PMID 14609996. Research Blogging.
- (2011) "C-reactive protein concentration and the vascular benefits of statin therapy: an analysis of 20 536 patients in the Heart Protection Study.". Lancet 377 (9764): 469-76. DOI:10.1016/S0140-6736(10)62174-5. PMID 21277016. Research Blogging.
- Hickling S, Hung J, Knuiman M, Divitini M, Beilby J (July 2008). "Are the associations between diet and C-reactive protein independent of obesity?". Prev Med 47 (1): 71–6. DOI:10.1016/j.ypmed.2008.02.007. PMID 18329089. Research Blogging.
- Solheim S, Arnesen H, Eikvar L, Hurlen M, Seljeflot I (October 2003). "Influence of aspirin on inflammatory markers in patients after acute myocardial infarction". Am. J. Cardiol. 92 (7): 843–5. PMID 14516890.
- Ridker PM, Rifai N, Clearfield M, et al (June 2001). "Measurement of C-reactive protein for the targeting of statin therapy in the primary prevention of acute coronary events". N. Engl. J. Med. 344 (26): 1959–65. PMID 11430324.
- Fisher M, Cushman M, Knappertz V, Howard G (July 2008). "An assessment of the joint associations of aspirin and statin use with C-reactive protein concentration". Am. Heart J. 156 (1): 106–11. DOI:10.1016/j.ahj.2007.12.035. PMID 18585504. Research Blogging.
- Ridker PM, Cushman M, Stampfer MJ, Tracy RP, Hennekens CH (April 1997). "Inflammation, aspirin, and the risk of cardiovascular disease in apparently healthy men". N. Engl. J. Med. 336 (14): 973–9. PMID 9077376.