Home :: Erythrocyte sedimentation rate

Erythrocyte Sedimentation Rate Test

Alternate Names : Sed Rate, Sedimentation Rate, ESR

The erythrocyte sedimentation rate (ESR) measures the degree of erythrocyte settling in a blood sample during a specified time period. The ESR is a sensitive but nonspecific test that is frequently the earliest indicator of disease when other chemical or physical signs are normal. The ESR commonly increases significantly in widespread inflammatory disorders; elevations may be prolonged in localized inflammation and malignant disease.

Purpose

• To monitor inflammatory or malignant disease.
• To aid detection and diagnosis of occult disease, such as tuberculosis, tissue necrosis, or connective tissue disease.

Patient preparation

• Explain to the patient that this test is used to evaluate the condition of red blood cells.
• Tell him that a blood sample will be taken. Explain who will perform the venipuncture and when.
• Reassure him that drawing a blood sample will take less than 3 minutes.
• Explain that he may feel slight discomfort from the tourniquet pressure and the needle puncture.
• Inform the patient that food or fluids need not be restricted before the test.

Procedure and posttest care

• Perform a venipuncture, and collect the sample in a 7-ml lavender-top, 4.5­ml black-top, or 4.5-ml blue-top tube. Check with the laboratory to determine it's preference.
• If a hematoma develops at the venipuncture site, apply warm soaks.

Precautions

• Completely fill the collection tube, and invert it gently several times to thoroughly mix the sample and the anticoagulant.
• Because prolonged standing decreases the ESR, examine the sample for dots or clumps and send it to the laboratory immediately. It must be tested within 2 hours.
• Handle the sample gently to prevent hemolysis.

Reference values

The ESR normally ranges from 0 to 15 mm/hour in males, 0 to 20 mm/hour in females, and 0 to to mm/hour in children. Rates gradually increase with age.

Abnormal findings

The ESR rises in pregnancy, anemia, acute or chronic inflammation, tuberculosis, paraproteinemias (especially multiple myeloma and Waldenstrom's macroglobulinemia), rheumatic fever, rheumatoid arthritis, and some malignant diseases.

Polycythemia, sickle cell anemia, hyperviscosity, and low plasma fibrinogen or globulin levels tend to depress the ESR.

Interfering factors

• Failure to use the proper anticoagulant, to adequately mix the sample and the anticoagulant, or to send the sample to the laboratory immediately.
• Hemolysis due to rough handling or excessive mixing of the sample insomnia and impotence.
• Hemoconcentration due to prolonged tourniquet constriction.
• Testing delayed more than 3 hours after sample collection (possible decrease).

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