C-reactive protein test (CRP, High-sensitivity C-reactive protein [hs-CRP], Ultra-sensitive CRP)
المؤلف:
Kathleen Deska Pagana, Timothy J. Pagana, Theresa Noel Pagana.
المصدر:
Mosbys diagnostic and laboratory test reference
الجزء والصفحة:
15th edition , p302-303
2025-11-29
9
Type of test Blood
Normal findings
< 1.0 mg/dL or < 10.0 mg/L (SI units)
Cardiac risk:
Low: < 1.0 mg/dL
Average: 1.0-3.0 mg/dL
High: > 3.0 mg/dL
hs-CRP: < 3 mg/L
Test explanation and related physiology
CRP is a nonspecific, acute-phase reactant used to diagnose bacterial infectious disease and inflammatory disorders, such as acute rheumatic fever and rheumatoid arthritis. CRP levels do not consistently rise with viral infections. CRP is a protein produced primarily by the liver during an acute inflammatory process and other diseases. A positive test result indicates the presence but not the cause of the disease. The synthesis of CRP is initiated by antigen–immune complexes, bacteria, fungi, and trauma.
The CRP test is a more sensitive and rapidly responding indicator than the erythrocyte sedimentation rate (ESR, p. 380). In an acute inflammatory change, CRP shows an earlier and more intense increase than ESR; with recovery, the disappearance of CRP precedes the return of ESR to normal.
The level of CRP correlates with peak levels of the muscle/ brain (MB) isoenzyme of creatine kinase, but CRP peaks occur 1 to 3 days later. Failure of CRP to normalize may indicate ongoing damage to the heart tissue. The level of CRP is a stronger predictor of cardiovascular events than the LDL cholesterol level. However, when used together with the lipid profile (in cholesterol), it adds prognostic information to that conveyed by the Framingham risk score.
The development of an assay for high-sensitivity CRP (hs CRP) has enabled accurate assays at even low levels. Because of the individual variability in hs-CRP, two separate measurements are required to classify a person’s risk level. In patients with stable coronary disease or acute coronary syndromes, hs-CRP measurement may be useful as an independent marker for assessing the likelihood of harmful events, including death, myocardial infarction, or restenosis after percutaneous coronary intervention.
Interfering factors
• Elevated test results can occur in patients with hypertension, elevated body mass index, metabolic syndrome or diabetes mellitus, chronic infection (e.g., gingivitis, bronchitis), chronic inflammation (e.g., rheumatoid arthritis), and low HDL or high triglycerides.
• Cigarette smoking can cause increased levels.
• Decreased test levels can result from moderate alcohol consumption, weight loss, and increased activity/exercise.
* Drugs that may cause increased test results include estrogens and progesterones.
* Drugs that may cause decreased test results include fibrates, niacin, and statins.
Procedure and patient care
• See inside front cover for Routine Blood Testing.
• Fasting: verify with laboratory
• Blood tube commonly used: red
Abnormal findings
Increased levels
- Arthritis
- Acute rheumatic fever
- Reiter syndrome
- Crohn disease
- Vasculitis syndrome
- Systemic lupus erythematosus
- Tissue infarction or damage
- Acute myocardial infarction
- Pulmonary infarction
- Kidney transplant rejection
- Bone marrow transplant rejection
- Soft tissue trauma
- Bacterial infection
- Postoperative wound infection
- Urinary tract infection
- Tuberculosis
- Malignant disease
- Bacterial meningitis
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