C-REACTIVE PROTEIN
Discovered by Tillett & Francis in 1930. First
identified as a substance in the serum with acute inflammation that reacted
with the "c" carbohydrate Ab of the capsule of pneumococcus.
CRP is a pentameric protein synthesized by the liver, whose level rises in response to inflammation. CRP is an acute-phase reactant protein that is primarily induced by the IL-6 action on the gene responsible for the transcription of CRP during the acute phase of an inflammatory/infectious process.
Lab values vary, and there is no standard at present. However, in general, the result is reported in either mg/dL or mg/L. Hs-CRP is usually reported in mg/L.
Interpretation of CRP levels:
- Less than 0.3 mg/L: Normal (level seen in most healthy adults).
- 0.3 to 1.0 mg/L: Normal or minor elevation (can be seen in obesity, pregnancy, depression, diabetes, common cold, gingivitis, periodontitis, sedentary lifestyle, cigarette smoking, and genetic polymorphisms).
- 1.0 to 10.0 mg/L: Moderate elevation (Systemic inflammation such as RA, SLE, or other autoimmune diseases, malignancies, myocardial infarction, pancreatitis, bronchitis).
- More than 10.0 mg/L: Marked elevation (Acute bacterial infections, viral infections, systemic vasculitis, major trauma).
- More than 50.0 mg/L: Severe elevation (Acute bacterial infections).
Certain medications, such as NSAIDs will falsely decrease
CRP levels. Statins, as well, have been known to reduce CRP levels falsely.
Recent injury or illness can falsely elevate levels, particularly when using
this test for cardiac risk stratification. Magnesium supplementation also can
decrease CRP levels.
As mentioned above, mild elevations in CRP can be seen without any systemic or inflammatory disease. Females and elderly patients have higher levels of CRP. Obesity, insomnia, depression, smoking, and diabetes can all contribute to mild elevations in CRP, and the results shall be interpreted with caution in individuals with these comorbidities.
Satyendra Dhar MD,
