Erythrocyte Sedimentation Rate (ESR) Test
The erythrocyte sedimentation rate is an indicator of inflammation in the body, and is therefore analyzed to help diagnose diseases when patients present symptoms or to assess the progression of chronic conditions.
General Description
The erythrocyte sedimentation rate (ESR) is a test included in blood analyses to identify the presence of inflammatory activity in the body. Also known as the erythrocyte sedimentation rate (ESR test), it is performed by measuring how quickly red blood cells (erythrocytes) in an anticoagulated blood sample settle at the bottom of a test tube over the course of one hour. When inflammation is present, erythrocytes tend to clump together, forming heavier aggregates that sediment more rapidly.
Although a high ESR can indicate inflammation, the results must be interpreted alongside other tests to establish a diagnosis. Moreover, it is a useful procedure for monitoring chronic inflammatory diseases.
When is it indicated?
The erythrocyte sedimentation rate test is often requested as part of routine blood analyses to assess the patient’s general health status. In addition, it provides valuable information in the following situations:
- Suspected inflammation due to symptoms such as fever and muscle or joint pain.
- Diagnosis of inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus, vasculitis, polymyalgia rheumatica, giant cell arteritis, or cancer.
- Monitoring certain treatments.
- Assessing the body’s inflammatory response.
How is it performed?
To measure the erythrocyte sedimentation rate, a blood sample is collected. The procedure is as follows:
- The patient extends their arm while seated or lying down.
- The fist is tightened and a tourniquet is applied above the elbow.
- The area is disinfected and a needle is inserted into one of the arm veins.
- The hand is opened and the tourniquet removed.
- Blood is collected into an ESR tube with a black cap. This tube contains a buffered sodium citrate solution that acts as an anticoagulant, ensuring the blood remains liquid and the results are reliable.
To perform the ESR test, the tube is placed in a strictly vertical, vibration-free position, graduated from 0 to 200 mm, and the distance traveled by the red blood cells in one hour is measured. Results are expressed in millimeters per hour (mm/h).
Risks
The ESR test does not pose health risks, although blood sampling may cause a bruise.
What to expect from an erythrocyte sedimentation rate test
On the day of blood collection, it is recommended to wear clothing that allows easy access to the arm. During the procedure, it is normal to feel a brief sting when the needle is inserted, but the discomfort is mild and short-lived. To prevent bruising, pressure should be applied to the puncture site for a few minutes. Once the sample has been collected, the patient may resume normal daily activities.
ESR results are typically available within one to two days. Normal values are considered to be 0–15 mm/h for women and 0–10 mm/h for men. However, these values must be evaluated by a specialist, taking additional factors into account, as certain circumstances may increase the sedimentation rate without indicating an infection. Examples include age, pregnancy, anemia, kidney problems, and obesity.
Specialties that request the erythrocyte sedimentation rate test
The ESR analysis is performed in the laboratory by Clinical analyses specialists upon request from various departments, such as Family and community medicine, Pediatrics, Rheumatology, and Immunology, as it is a very common test.
How to prepare
No special preparation is required for an erythrocyte sedimentation rate test. However, as other analyses are often requested at the same time, fasting and avoiding smoking prior to blood collection may be necessary to prevent altered results.
