Erythrocyte Sedimentation Rate (ESR)

Introduction

Erythrocyte Sedimentation Rate (ESR) is a common blood test used to detect and monitor inflammation in the body. It measures how quickly red blood cells settle to the bottom of a vertical tube containing blood during a specific period, usually one hour.

Normally, red blood cells settle relatively slowly. During inflammation, certain proteins in the blood increase and cause red blood cells to stick together. These groups of cells settle faster, resulting in an increased ESR.

ESR is a simple, inexpensive, and widely available laboratory test. However, it is a nonspecific test, meaning that an increased ESR cannot identify one particular disease by itself.

What is ESR?

Erythrocyte Sedimentation Rate (ESR) is the rate at which red blood cells settle in a vertical column of anticoagulated blood during a specified period.

The result is usually expressed as millimeters per hour (mm/hour).

For example, an ESR result of 25 mm/hour means that the red blood cells have settled sufficiently to produce a 25-mm plasma column after one hour.

Principle of ESR

The principle of ESR is based on the settling of red blood cells under the influence of gravity.

Normally, RBCs have a negative surface charge that keeps them separated. During inflammation, plasma proteins such as fibrinogen increase. These proteins reduce the repulsive forces between RBCs and promote the formation of stacks called rouleaux.

Rouleaux formations are heavier and settle more rapidly than individual RBCs. Therefore, increased rouleaux formation usually results in an increased ESR.

Basic Principle

Inflammation → Increased plasma proteins → Rouleaux formation → Faster RBC settling → Increased ESR

Why is ESR Performed?

1. Detection of Inflammation

ESR can provide supportive evidence that an inflammatory process may be occurring somewhere in the body.

2. Monitoring Inflammatory Diseases

ESR can be used to monitor certain chronic inflammatory and autoimmune conditions over time.

3. Monitoring Treatment

Changes in ESR may provide information about changes in inflammatory activity during treatment.

4. Supporting Diagnosis

ESR can support the evaluation of some inflammatory, infectious, and autoimmune diseases when combined with other clinical findings.

5. Investigation of Unexplained Symptoms

ESR may be requested during the investigation of unexplained fever, joint symptoms, fatigue, and other clinical problems.

Sample Required for ESR

ESR requires a blood sample. For the traditional Westergren method, venous blood is usually collected into a tube containing an appropriate anticoagulant.

The blood sample should be properly collected, mixed, and handled before testing to obtain a reliable result.

Methods of ESR Testing

Several methods have been used to measure ESR. The most widely recognized traditional method is the Westergren method.

Westergren Method

The Westergren method is commonly used as the reference method for ESR measurement. In this method, anticoagulated blood is placed into a long, graduated tube and allowed to stand vertically without disturbance.

After one hour, the height of the clear plasma column is measured and reported in mm/hour.

Procedure

Collect the required blood sample.

Mix the blood properly with the appropriate anticoagulant.

Fill the ESR tube according to the method requirements.

Place the tube in a completely vertical position.

Allow the blood to remain undisturbed for one hour.

Measure the height of the clear plasma column.

Record the result in mm/hour.

Stages of Erythrocyte Sedimentation

1. Rouleaux Formation

Red blood cells begin to form stacks or aggregates due to changes in plasma proteins.

2. Sedimentation

The aggregated red blood cells settle downward at an increasing rate.

3. Packing

The red blood cells become more closely packed at the bottom of the tube.

Normal ESR Values

There is no single normal ESR value for everyone. Reference ranges may vary depending on age, sex, laboratory method, and other factors.

Typical adult reference ranges may be approximately:

Group	Approximate ESR
Adult males	0–15 mm/hour
Adult females	0–20 mm/hour
Older adults	May be somewhat higher
Children	Generally lower than adults

Important: The reference range provided by the individual laboratory should be used when interpreting an ESR report.

What Does a High ESR Mean?

A high ESR means that red blood cells are settling faster than expected.

An increased ESR may occur in:

Infections
Inflammatory diseases
Autoimmune disorders
Rheumatoid arthritis
Some connective tissue diseases
Kidney diseases
Certain cancers
Anemia
Tissue injury

However, a high ESR does not automatically indicate a serious disease because ESR is a nonspecific test.

What Does a Low ESR Mean?

A low ESR is generally less clinically significant than an elevated ESR.

A low ESR may be associated with certain blood disorders, abnormal red blood cell shapes, increased red blood cell concentration, and some changes in plasma proteins.

Factors Affecting ESR

Biological Factors

Several biological factors can influence ESR.

Age
Sex
Pregnancy
Anemia
Certain medications
Menstrual status

Blood-Related Factors

The following blood characteristics can affect ESR:

Red blood cell size
Red blood cell shape
Red blood cell concentration
Plasma protein levels

Technical Factors

Incorrect laboratory technique can also affect ESR results.

Temperature
Tube position
Testing time
Sample handling
Anticoagulant concentration
Vibration or movement of the tube

ESR and Infection

ESR can increase during many infections because infection may produce an inflammatory response.

However, ESR alone cannot determine the exact cause of infection, the specific microorganism responsible, or the location of infection.

Additional laboratory tests and clinical assessment are usually required.

ESR in Autoimmune Diseases

ESR can be elevated in several autoimmune and inflammatory diseases.

Examples include:

Rheumatoid arthritis
Systemic lupus erythematosus
Temporal arteritis
Polymyalgia rheumatica
Other connective tissue diseases

Repeated ESR measurements may sometimes be useful for monitoring inflammatory activity over time.

ESR vs CRP

C-reactive protein (CRP) is another commonly used marker of inflammation.

Feature	ESR	CRP
Full form	Erythrocyte Sedimentation Rate	C-Reactive Protein
Measures	Rate of RBC settling	CRP concentration
Type	Indirect inflammatory marker	Acute-phase protein
Effect of anemia	Can increase ESR	Usually less affected
Response	Relatively slower	Generally faster
Specificity	Low	Low
Common use	Monitoring inflammation	Detecting and monitoring inflammation

Both tests have advantages and limitations, and the appropriate test depends on the clinical situation.

Advantages of ESR

1. Simple Test

ESR is relatively simple to perform in a clinical laboratory.

2. Inexpensive

The test is generally inexpensive compared with many other laboratory investigations.

3. Widely Available

ESR testing is available in many hospitals and diagnostic laboratories.

4. Useful for Monitoring

It can help monitor certain inflammatory conditions over time.

5. Requires a Blood Sample

Only a blood sample is required for performing the test.

6. Provides Supportive Information

ESR can provide useful supportive information when interpreted together with other clinical findings.

Limitations of ESR

1. Nonspecific Test

An increased ESR does not identify a specific disease.

2. Many Factors Affect the Result

Age, anemia, pregnancy, medications, and RBC characteristics can influence ESR.

3. Slow Response

ESR may change more slowly than some other inflammatory markers.

4. Normal ESR Does Not Exclude Disease

Some inflammatory conditions may occur even when ESR is within the normal reference range.

5. High ESR Does Not Always Mean Severe Disease

A high ESR should not be interpreted as proof of severe disease without considering other clinical findings.

ESR Test Procedure in the Laboratory

Step 1: Blood Collection

Collect the required venous blood sample using the appropriate anticoagulant.

Step 2: Mixing

Mix the blood sample gently and adequately.

Step 3: Filling the Tube

Fill the ESR tube according to the laboratory method.

Step 4: Positioning

Place the tube in a completely vertical position.

Step 5: Sedimentation

Allow the blood to remain undisturbed for the required period, usually one hour.

Step 6: Reading

Measure the height of the clear plasma column.

Step 7: Reporting

Report the result in mm/hour.

Step 8: Interpretation

Compare the result with the laboratory reference range and other clinical findings.

Precautions During ESR Testing

1. Proper Sample Collection

Use a properly collected blood sample for accurate testing.

2. Correct Anticoagulant

Use the appropriate anticoagulant and maintain the correct blood-to-anticoagulant ratio.

3. Proper Mixing

Mix the blood sample adequately before filling the ESR tube.

4. Vertical Position

Keep the ESR tube completely vertical during sedimentation.

5. Avoid Movement

Avoid vibration, shaking, or movement of the tube during the test.

6. Correct Timing

Read the ESR at the specified time, usually after one hour.

7. Proper Temperature

Avoid excessive temperature changes during testing.

8. Follow Laboratory Guidelines

Always follow the laboratory's standard operating procedure.

Clinical Importance of ESR

ESR remains a useful supportive laboratory investigation. It may help healthcare professionals detect possible inflammatory activity, monitor certain chronic inflammatory diseases, and follow changes over time.

However, ESR should not be interpreted as an isolated diagnostic test. It should be evaluated together with symptoms, medical history, physical examination, and other laboratory results.

Frequently Asked Questions (FAQs)

What is ESR?

ESR stands for Erythrocyte Sedimentation Rate. It measures how quickly red blood cells settle in a blood sample during a specified period.

What is the unit of ESR?

ESR is usually reported in millimeters per hour (mm/hour).

Is ESR a diagnostic test?

ESR is mainly a nonspecific marker of inflammation. It can support diagnosis but cannot usually identify a specific disease by itself.

What causes high ESR?

Infections, inflammatory diseases, autoimmune disorders, anemia, and several other conditions can increase ESR.

Is a high ESR always dangerous?

No. A high ESR does not necessarily indicate a serious disease. The result should be interpreted with symptoms and other test results.

What is the difference between ESR and CRP?

ESR measures the rate of red blood cell settling, while CRP measures the concentration of C-reactive protein in the blood.

How long does an ESR test take?

The traditional Westergren ESR test requires approximately one hour for the sedimentation period.

Conclusion

Erythrocyte Sedimentation Rate (ESR) is a simple, inexpensive, and widely used blood test that provides supportive information about inflammation in the body.

The test is based on the rate at which red blood cells settle in a vertical column of blood. Increased plasma proteins during inflammation promote rouleaux formation, causing RBCs to settle more rapidly and resulting in an increased ESR.

Although ESR is useful in evaluating and monitoring many inflammatory conditions, it is nonspecific and cannot identify a particular disease by itself. Therefore, ESR results should always be interpreted together with clinical symptoms, medical history, physical examination, and other laboratory investigations.