Synonym

• CRP

Tubes

• Red, tiger, marigold, or green top tube
• 5-7 mL venous blood

Additional information

• Avoid fluids, except water, 8-12 hrs before test when test is done electively
• Handle sample gently to prevent hemolysis

Info

• The C-reactive protein (CRP) test is a quantitative analysis of CRP in the blood
• CRP is an indicator of acute inflammation
• CRP got its name due to its ability to precipitate the somatic C-polysaccharide of Streptococcus pneumoniae
• CRP is a glycoprotein synthesized primarily in the liver in response to increased interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-µ) concentration
• CRP is found in body fluids include fluid from the pleural space, peritoneum, pericardium and synovium
• CRP is one of the most sensitive acute-phase reactants
• The CRP assay is a nonspecific test that determines the presence, and not the cause, of inflammation

Clinical

Clinical Overview:

C-Reactive protein (CRP) is usually ordered to assist in the evaluation of whether a serious bacterial infection is present (most commonly in infants and children). An elevated CRP is utilized as part of an overall clinical assessment as a normal level doesn't completely rule out serious bacterial infection and an elevated level can occur for reasons other than serious bacterial infection (including viral infections).

C-Reactive protein assay may be useful in the following conditions:

• Detection of infection or inflammation and monitoring response to therapy
• Bacterial infections (used most commonly in neonates and children)
• Evaluation of necrotizing enterocolitis in neonates
• Monitoring response to therapy for infections as in endocarditis, osteomyelitis
• Postoperative infections (Surgery elevates CRP, but this returns to normal levels ~ 7 days post operatively)
• Appendicitis
• Acute pelvic inflammatory disease
• Systemic lupus erythematosus versus rheumatoid arthritis
• Crohn's disease versus ulcerative colitis
• Pyelonephritis versus cystitis
• Chorioamnionitis
• Note that a normal CRP doesn't rule out serious bacterial infection; but simply makes it less probable
• Patients with coronary artery disease
• Detection of short term and long term risk for adverse outcome in acute coronary syndromes (ACS) [Note that hsCRP is a better test for this]

• Screening for disease
• Infections
• Inflammatory diseases
• Neoplastic diseases
• Tissue injury
• Detection and evaluation of inflammatory disorders
• Inflammatory bowel disease
• Reiter's syndrome
• Rheumatic fever
• Rheumatoid arthritis
• Vasculitic syndromes
• Detection, evaluation, and progress of tissue injury and neoplasia
• Burkitt's lymphoma
• Myocardial infarction
• Pulmonary embolism
• Transplant rejection
• To monitor wound healing process of internal incisions, burns, and organ transplantation
• To help interpret elevated ESR (Erythroid sedimentation rate)
• CRP responds within 6-10 hrs of inflammation and has a short half-life of 5-7 hrs, making it particularly useful in the first 24 hours of the disease process
• CRP levels increase before ESR or antibody titers, and also decline before the ESR levels fall

Additional information

• High-sensitivity CRP assay (hs-CRP) can detect lower levels of CRP, which can be useful in the assessment of risk for developing coronary artery disease. The hs-CRP has very high sensitivity with a detection limit as low as 0.01 mg/dL
• Recent studies have indicated the elevated levels of CRP is related to the development of age-related macular degeneration (AMD) and increased risk of colon cancer
• Related laboratory tests include:
• Apolipoprotein A and B
• Aspartate aminotransferase
• Atrial natriuretic peptide
• Blood gases
• B-type natriuretic peptide
• Calcium (blood and ionized)
• Cholesterol (total, HDL, and LDL)
• Creatine kinase and isoenzymes
• Cultures of blood, CSF, urine, wound
• ESR
• Homocysteine
• Lactate dehydrogenase and isoenzymes
• Myoglobin
• Procalcitonin
• Troponin
• White blood cell count

Nl Result

Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.

High Result

Conditions associated with elevated CRP levels include:

• Acute bacterial and viral infections (usually elevated in bacterial, occassionally in viral)
• Cancer (Active, widespread)
• Crohn's disease
• Hodgkin's disease
• Inflammatory bowel disease
• Intrauterine contraceptive devices
• Myocardial infarction
• Obesity
• Postoperative (declines after 4^th, normal by 7^th day)
• Pregnancy (third trimester)
• Rheumatic fever
• Rheumatoid arthritis
• Syndrome X - metabolic syndrome
• Systemic lupus erythematosus (SLE)
• Tuberculosis
• Drugs
• Anabolic steroids
• Oral contraceptives

Low Result

• Inhibitory cytokines and exercise decrease the CRP levels
• Drugs that reduce the CRP levels include:
• Aurothiomalate
• Corticosteroids (Dexamethasone, Prednisone, etc)
• Methotrexate
• Nonsteroidal anti-inflammatory drugs
• Penicillamine
• Pentopril
• Salicylates
• Statin drugs
• Sulfasalazine

References

• Danesh J et al. C-Reactive Protein and Other Circulating Markers of Inflammation in the Prediction of Coronary Heart Disease. The New England Journal of Medicine. 2004 April 1; Volume 350:1387-1397.
• Gruenewald TR et al. From the Cover: Combinations of biomarkers predictive of later life mortality. Proc Natl Acad Sci U S A. 2006 Sep 19;103(38):14158-63. Epub 2006 Sep 18.
• Gunter MJ et al. A prospective study of serum C-reactive protein and colorectal cancer risk in men. Cancer Res. 2006 Feb 15;66(4):2483-7.
• Hawkins RC et al. Should high sensitive C-reactive protein measurement be included in health screening packages? Singapore Med J. 2006 Oct;47(10):837-40.
• LabTestsOnline®. C-Reactive Protein. [Homepage on the Internet] © 2001-2006. Last reviewed on September 3, 2004. Last accessed on January 25, 2007. Available at URL: http://www.labtestsonline.org/understanding/analytes/crp/test.html
• Makhoul IR et al. Values of C-reactive protein, procalcitonin, and Staphylococcus-specific PCR in neonatal late-onset sepsis. Acta Paediatr. 2006 Oct;95(10):1218-23.
• Pourcyrous Massroor et al. C-Reactive Protein in the Diagnosis, Management, and Prognosis of Neonatal Necrotizing Enterocolitis. Pediatrics. 2005 November;116(5):1064-1069.
• Schillaci G et al. C-reactive protein in hypertension: clinical significance and predictive value. Nutr metab Cardiovasc Dis. 2006 Sep 14; [Epub ahead of print].
• Seddon JM et al. Progression of age-related macular degeneration: prospective assessment of C-reactive protein, interleukin 6, and other cardiovascular biomarkers. Arch Ophthalmol. 2005 Jun;123(6):774-82.
• Selim G et al. Inflammation predicts all-cause and cardiovascular mortality in haemodialysis patients. Prilozi. 2006;27(1):133-44.
• Shadick NA et al. C-reactive protein in the prediction of rheumatoid arthritis in women. Arch Inern Med. 2006 Dec 11-25;166(22):2490-4.
• Tatsuo Kono et al. Negative C-reactive protein in children with bacterial infection. Pediatrics International. 1999 October. 41(5):496-499.
• Thalmaier D et al. The +1059G/C polymorphism in the C-reactive protein (CRP) gene is associated with involvement of the terminal ileum and decreased serum CRP levels in patients with Crohn's disease. Aliment Pharmacol Ther. 2006 Oct 1;24(7):1105-15.
• UTMB Laboratory Survival Guide®. C-REACTIVE PROTEIN, serum. [Homepage on the Internet]© 2006. Last reviewed in February, 2006. Last accessed on January 25, 2007. Available at URL: http://www.utmb.edu/lsg/LabSurvivalGuide/chem/C_REACTIVE_PROTEIN.htm