What Is the Connection Between CRP and Infection?

C-reactive protein (CRP) is a proteinaceous substance discovered by Tillet and Francis in 1930. They initially observed that the serum of some acute patients could react with the capsular C-polysaccharide of Streptococcus pneumoniae. It was subsequently confirmed that the substance capable of reacting with C-polysaccharide was a protein.

C-reactive protein (CRP)

CRP is an acute phase protein synthesized by liver cells when the body is exposed to inflammatory stimuli such as microbial invasion or tissue damage.

Note: Acute phase reactions include changes in certain serum protein concentrations during infection, inflammation, and trauma. These proteins include, in addition to CRP,

CRP is the body

CRP increases within a few hours of the onset of inflammation, reaching a peak within 48 hours, and decreases to normal levels as the lesion subsides and tissue, structure, and function recover. This response was not affected by radiotherapy, chemotherapy, or corticosteroids. Therefore, the detection of CRP is widely used in clinical applications, including the diagnosis and differential diagnosis of acute infectious diseases, the monitoring of postoperative infections; the observation of the efficacy of antibiotics; the detection of disease course and the prognosis. Its clinical applications are as follows:

[Evaluation of disease activity and efficacy monitoring]

The degree of CRP elevation reflects the size or activity of inflammatory tissues. In acute inflammation and infection, CRP has a good correlation with disease activity. This condition is not compatible with chronic inflammation, although in some important cases, such as rheumatoid arthritis, segmental ileitis, and rheumatic polymyalgia, this correlation is sufficient for therapeutic monitoring.

1, CRP value of 10-50mg / L indicates mild inflammation, such as local bacterial infections (such as cystitis, bronchitis, abscess), surgery and accidental trauma, myocardial infarction, deep vein thrombosis, inactive connective tissue disease Many malignancies and most viral infections.

2. CRP value rising to about 100mg / L indicates a more serious disease, and its degree of inflammation requires intravenous injection if necessary.

3. A CRP value greater than 100 mg / L indicates a serious disease process and often indicates the presence of a bacterial infection.

CRP kinetic response:

The increase of CRP value lags about 12 hours after the change of inflammatory activity. But it is important to detect changes earlier than clinical symptoms, such as 4-6 weeks earlier in rheumatoid arthritis. Therefore, the CRP value can provide a method for rapid clinical decision. Continuously rising CRP values generally prove ineffective treatment, and treatment regimens should be changed.

CRP measurement can be used to monitor the treatment of the following conditions:

* In many acute infections, as the basis for the most effective antibiotic treatment.

* Antibiotic treatment when high-risk patients lack a microbiological diagnosis.

* Interrupt antibiotic therapy when CRP drops to normal.

* Determine the dose of anti-inflammatory drugs based on changes in CRP levels.

* In some rheumatic diseases that are difficult to clinically evaluate, quickly select the appropriate anti-rheumatic treatment.

* Estimated onset of complications. Such as the development of giant cell arteritis in patients with rheumatic polymyalgia.

[Application of serum CRP measurement in common diseases]

1. Adult postoperative stage:

All types of surgery cause inflammation, and the acute phase response is roughly proportional to the degree of tissue damage. In the uncomplicated medical history, CRP reached 10 mg / L at about 6 hours, rarely exceeded 150 mg / L at the peak of 48 hours, and dropped to baseline at 7-10 days. Postoperative complications such as infections, tissue necrosis, and hematomas such as thrombosis, depending on the time of occurrence, CRP will remain elevated or cause secondary elevation after 48 hours. In many cases, the elevation of CRP is more than 24 hours earlier than the clinical diagnosis of complex pathology. Patients at risk (more than 10% of patients with partial colectomy) should be monitored by daily CRP measurements. For diagnosis of deep vein thrombosis consistent with clinical interpretation, the literature reports that the CRP assay has a sensitivity of 100% and a specificity of about 52%.

2. Acute pancreatitis:

Acute pancreatitis usually causes an increase in CRP in the first 24 hours, and if there are no complications, this value decreases during the first weekend. If CRP is greater than 100 mg / L at this time, complications such as cysts or pseudocysts are likely to have occurred, which can be confirmed by ultrasound and radiological examination. If the CRP is greater than 110 mg / L at the time of admission, it may be hemorrhagic pancreatitis (clinical sensitivity 88%, specificity 94%).

3. Genital infection, pelvic inflammatory disease:

Infection with uncomplicated chlamydia such as Neisseria gonorrhoeae does not cause an increase in CRP, but it spreads to the pelvic tissues and can cause acute phase reactions from acute or chronic pelvic inflammatory disease. In one study, 81% of cases of uterine appendicitis had elevated CRP and only 52% had leukocytosis, so CRP could be considered as valuable data for examining this patient.

4. Appendicitis:

Using 10 mg / L as the cut-off value, it has been reported that the clinical sensitivity of CRP is 68.2%, and the specificity is 75.1%. The neutrophils increased with 87.2 and 63%.

5. Lung infection:

Pneumonia is more difficult to diagnose in older people and usually has less fever. In many cases, CRP is greater than 100 mg / L, which strongly suggests bacterial infections such as pneumonia or suppurative bronchitis. Typical viral pneumonia does not exceed 50 mg / L.

6, children with fever:

Although fever is most common in children, it is difficult to distinguish it from bacterial sepsis, such as otitis media, tracheitis, tonsillitis, and cystitis, and antibiotics are not necessary. Results show that CRP is significantly higher than 40 mg / L in children with a patient older than 12 hours. The sensitivity of the diagnosis of bacterial infection is 79% and the specificity is 90%. If the ESR greatly exceeds 30mm / h, the sensitivity is 97% and the specificity is 89%, which should be paid attention to.

7. Myocardial infarction:

Myocardial infarction is usually associated with elevated CRP concentrations, which often occur within the first few hours of pain and typically peak at 3-4 days. CRP also returned to normal 7-10d after CK-MB returned to normal. Elevated CRP levels in the presence of suggestive symptoms are a sensitive indicator of this condition. In acute myocardial infarction, this condition occurred in 49 of 50 people, and significant changes in electrocardiogram Q waves occurred in all 100 people. The increase after 10 days indicated complications and poor prognosis. The latest data show that high circulating CRP predicts the development of coronary heart disease in patients with stable or unstable angina pectoris.

8. Gouty arthritis:

Elevation of mild to severe CRP is more common in gout, but less elevated in pseudogout.

9. Osteoarthritis:

In this case, CRP elevation is mainly degenerative rather than inflammation.

10. Gastrointestinal diseases, intestinal inflammatory diseases:

Active stage gastroenteritis is accompanied by elevated CRP associated with disease activity and can be used for therapeutic monitoring. Ulcerative colitis is associated with normal or slightly elevated CRP of less than 50 mg / L. Allergic bowel syndrome is a functional disease that is not associated with inflammation and does not cause an increase in CRP.

11. Rheumatic polymyalgia:

This disease, characterized by middle age and above, is manifested by severe morning stiffness such as pain in the arm around the shoulder wound, which is associated with diffuse systemic symptoms such as compression and discomfort. Serum CRP and ESR usually appear elevated together, although often not in parallel, but they are a useful diagnosis in important diseases. Without treatment, about 30% of patients will develop supercranial arteritis with severe visual danger. CRP quickly returns to normal when responding to treatment with corticosteroids, and its detection is useful for monitoring and adjusting treatment. The ESR changes quickly.

12. Malignant tumors:

Fever and acute phase reactions are common features of a wide range of malignancies. This is due to the tumor itself releasing cytokines, macrophage infiltration or associated infection or tissue necrosis. Elevated and rising CRP levels are predictive of poor prognosis and often suggest metastatic spread. Among those malignant lymphomas, interleukin 6 is released from these tumors, notably multiple myeloma and Hodgkin's disease. If infection is ruled out, CRP levels are associated with prognosis and tumor spread. In this way, the CRP in asymptomatic Hodgkin's disease is not less than 20 mg / L, otherwise the CRP level can increase to the range of 150 mg / L when symptoms occur.

13. Connective tissue disease: CRP is associated with disease in patients with rheumatoid arthritis, and systemic lupus erythematosus (SLE) is poor. However, some reports suggest that CLE is increased in SLE, vasculitis, and myositis.

14. Transplantation: For monitoring rejection reactions, CRP has important coordinates. CRP decreased to normal 8 days after organ transplantation. If rejection occurred, serum creatinine, urine nitrogen and CRP all increased. Elevated CRP was reported to occur 4 days before rejection. However, infection can also cause elevated CRP. Care should be taken to distinguish between the two. During rejection, the anti-rejection CRP was increased with azaconazole, but not with cyclosporine A. It is thought that this is related to the suppression of T cells by angiosomes and a decrease in M activity. GVHD also has elevated CRP.

15. Pediatric infectious diseases: In children with acute lymphocytic leukemia, bacterial septicemia is common, and CRP exceeding 100 mg / L is considered a bacterial infection. Meningitis in children averages 195mg / L. In children with viral infections, CRP is much lower.

[Prognostic evaluation]

A continuously rising CRP value indicates no improvement in inflammation and is often evidence of treatment failure and poor prognosis. Such as malignant diseases, infections and myocardial infarction.