What is the Difference Between ESR and CRP

The main difference between ESR and CRP is that ESR is the rate at which red blood cells in anticoagulated whole blood descend in a standardized tube over a period of one hour whereas CRP is the measurement of the levels of C-reactive protein of blood by its reaction with an antigen-antibody complex. Furthermore, ESR is mainly important for the detection of the chronic phase of inflammation while CRP is important for the detection of the acute phase of the inflammation. In addition, ESR is less accurate, less sensitive, and a slow test while CRP is the most accurate, sensitive, a quick test. 

ESR (erythrocyte sedimentation rate) and CRP (C-reactive protein) are the two oldest and more common types of laboratory tests for the detection of inflammation in the body. Generally, inflammation can be either acute or chronic and it allows cells to release inflammatory mediators, generating pain in joints, muscle, discs, ligaments, tendons, fascia, etc.  

Key Areas Covered 

1. What is ESR
     – Definition, Method, Importance
2. What is CRP
     – Definition, Method, Importance
3. What are the Similarities Between ESR and CRP
     – Outline of Common Features
4. What is the Difference Between ESR and CRP
     – Comparison of Key Differences

Key Terms 

Acute Phase, Blood Tests, Chronic Phase, CRP, ESR, Fibrinogen, Inflammation

What is ESR 

ESR (erythrocyte sedimentation rate) is a common test for the detection of inflammation and pain. Further, it serves as the surrogate marker for the acute phase of inflammation. Because, the main components; the fibrinogen, alpha globulin, and other clotting proteins, that increase the sedimentation of red blood cells do not occur at the acute phase of the inflammation. 

Figure 1: A Rack with Ten ESRs in the Round-Style Tubes

In general, the main measurement of  ESR is the viscosity of the blood plasma, assessing the tendency for red blood cells to aggregate. In systemic inflammation, the blood levels of fibrinogen increase, and that in turn, allows the red blood cells to stick together. Thus, it results in an increased rate of sedimentation of red blood cells. Furthermore, the sedimentation rate also depends on the plasma albumin concentration, size, shape, and number of red blood cells, and non-acute phase reaction proteins, in particular, normal and abnormal immunoglobulins. In anaemia, a higher rate of ESR is present without an acute phase reaction. Besides, a higher ESR might occur in renal failure, obesity, ageing, and female sex.  

What is CRP 

CRP (C-reactive protein) is the other test for the detection of inflammation. It is more accurate, sensitive and quick. Also, CRP is a better marker for the detection of the acute phase of inflammation. Serum amyloid A protein and procalcitonin are the other two markers of acute phase inflammation. Sometimes, a 100-fold increase can be observed in both acute and chronic phases of inflammation. 

Figure 2: C-Reactive Protein

Moreover, in response to both acute and chronic inflammation, cytokines, mainly interleukin-6, is released into the bloodstream. As a consequent response, the liver releases CRP. In the innate immune response, it acts as an acute-phase reactant by attaching to microorganisms and damaged cellular components via phosphocholine. So, this activates both the phagocytosis and complement system. Therefore, CRP responds to inflammation quickly. However, the highest concentration of CRP occurs in less than two days of inflammation and the concentration falls rapidly with the resolving of the inflammation. 

Similarities Between ESR and CRP  

• ESR and CRP are the two most common types of blood tests for the detection of inflammation in the body.  
• Both are among the oldest blood tests.  
• Apart from the detection of inflammation and its pain, these tests are important for monitoring the effectiveness of treatment.    
• However, the values of both tests are high when pain is present and they reduce with the initiation of appropriate pain treatment.  
• Besides, both tests are less expensive and can be performed along with a complete blood count as well. 

Difference Between ESR and CRP 

Definition 

ESR (erythrocyte sedimentation rate) refers to the rate at which red blood cells in anticoagulated whole blood descend in a standardized tube over a period of one-hour. Meanwhile, CRP is the measurement of the levels of C-reactive protein of blood by its reaction with an antigen-antibody complex.  

Principle 

High amounts of fibrinogen released as a result of the inflammatory process cause red blood cells to stick together, and thus, increasing their sedimentation rate. On the other hand, the circulating concentration of CRP increases in response to inflammation.  

Detecting the Acute Phase  

ESR is less accurate to use for detecting the acute phase of inflammation, in comparison, as it does not test the acute phase markers. But, CRP is more accurate to use for detecting the acute phase of inflammation as the liver responds to the acute phase of inflammation by producing CRP. 

Importance 

In comparison, ESR is a less accurate and less sensitive test than the CRP, which is more accurate, sensitive, and is a quick test. 

Especial Occasions 

Moreover, ESR gives better results in low-grade bone and joint infections and in autoimmune disease, while CRP gives better results in systemic lupus erythematosus, concomitant bacterial infection, active serositis, and chronic synovitis.  

Conclusion 

ESR is one of the two common laboratory tests for the detection of inflammation in the body. Generally, inflammation results in the release of a higher amount of fibrinogen in its chronic phase. This fibrinogen causes red blood cells to stick, increasing the levels of red blood cell sedimentation. On the other hand, CRP is the other blood test for the detection of inflammation; especially, in the acute phase. Here, the liver produces a higher amount of CRP in response to inflammation, increasing the levels of circulating CRP. Therefore, the main difference between ESR and CRP is the principle behind each test. 

References:

1. Harrison, Michael. “Abnormal Laboratory Results: Erythrocyte Sedimentation Rate and C-Reactive Protein.” Australian Prescriber, vol. 38, no. 3, Jan. 2015, pp. 93–94., doi:10.18773/austprescr.2015.034.

Image Courtesy:

1. “Esrrack 350px” By The original uploader was Tristanb at English Wikipedia. (CC BY-SA 3.0) via Commons Wikimedia   
2. “PDB 1lj7 EBI” By Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute (Public Domain) via Commons Wikimedia